ARTIFICIAL WARMTH & VENTILATION, AND THE Cirwm ptos te tolritlv %e a« f wtoa. BV WM. C. BAKER, .AOTIOAL KSOIKIIB IN WAKMINO AND TINTIUIIN* REVISED EDITION. ♦ ■»» NEW YORK: PUBLISHED BY J. F. TROW, 60 GREENE ST. 1860. INTRODUCTORY REMARKS. There is no subject of a material nature to which such vital importance can with propriety be attached, as to that of the construction of our dwellings; for in them we are to live and find a home with our families and friends. And nothing connected with that home, its health, comfort, and happiness, can justly command the important considerations that are connected with the nuility of the air—the element upon which chiefly de- pends the existence of those most dear to us, our wives and children, who spend the greater part of their lives within doors. Hence the artificial heat, which may make that air impure, becomes a subject of paramount significance. In the Sun nature has kindly provided us with a magnificent warming apparatus, which alone, for a great portion of the globe, is all-sufficient. Through the day he diffuses genial and equal warmth, and at evening withdraws to permit the cool repose of the night. He crives a reflective and conductive heat, with the warmest rays nearest our feet, instead of our heads: the quality, too, is at once of the purest, and always below an ex- cessive temperature. But unfortunately for the inhabitants of that section of the earth in which we reside, the sun yields a suffi- cient external warmth but a small portion of the year, and we are compelled to resort to some artificial substi- tute for the remainder. We have that grand luminary 4 and heater for a model, and the nearer we imitato him the nearer shall we come to perfection in the construc- tion and application of artificial warming apparatus. In speaking of the most common contrivances for creating artificial warmth, it is admitted that they all possess, to a certain extent, the superficial object to be attained, viz. : heating power. But this is in reality but an elementary principle, therefore we shall speak of qualities that are not so apparent, and leave the reader to exercise his own judgment in determining which plan comes nearest to the standard of the great prototype, the Sun, and combines the qualities appertaining to a perfect system for creating and maintaining artificial heat. OPEN FIRES. One of the earliest modes for warming, and one which at the present time is more universally adopted than any other, is the burning of wood or coal in an open fire-place at one side of the room. There are various modifications of this arrangement, dating all the way back from the primitive andirons, or fire-dogs, within an uncouth fire-place of clay or stone, to the modern grate with its glittering surroundings of silver and' marble; but they are all subject to the following objec- tions. 1. Waste of fuel. It has been found that in a common open English fire, seven-eighths of the heat produced from the fuel ascend the chimney, and are absolutely lost. This lost fuel is thus accounted for. One half of the heat is carried off in the smoke from the burning mass, one quarter is carried off by the current of the warmed air of the room, which is constantly entering the chimney between the fire and the mantel-piece, and mixing with 5 the smoke lastly, one-eighth part of the combustible matter is supposed to form the black and visible part of smoke, in an unburned state. Some writers have even gone so far as to estimate the loss of heat in an open fire at fourteen-fifteenths of the whole. 2. Unequal heating at different distances from the fire.— This forms a remarkable contrast with the uniform tem- perature in the air of a summer afternoon. In rooms with a strong fire, in very cold weather, it is not uncommon for persons to complain of being " scorched" on one side, and " pierced with cold " on the other; this is particu- larly the case in large apartments ; for as the intensity of radiating heat (like light) is only one-fourth as great at a double distance, the walls of the room farthest from the fire are but little warmed, and therefore, reflect but little heat to the backs of persons grouped round the fire. 3. Cold draughts.—Air being constantly required to feed the fire, and to supply the chimney-draught, the fresh air which enters by the crevices and defects in the doors, windows, floors, &c, is often felt most injuriously as a cold current. " There is nothing more dangerous to health than to sit near such inlets, as is proved by the rheu- matism, stiff necks, and catarrhs, not to mention more serious diseases, which so frequently follow the exposure. There is an old Spanish proverb, thus translated : If cold wind reach you through a hole, Go make your will, and mind your soul, which is scarcely an exaggeration." The current of Lh air which enters to feed the fire becomes very re- markable when doors or windows are opened, for the « can tn* much more than it otherwise _ ffh,„ tie doors and windows are shut; and thus the 6 room with its chimney becomes like an open funnel, rapidly discharging its warmed air. 4. Cold to the feet.—The fresh air which enters in any case to supply the fire, being colder and specifically heav- ier than the general mass already in the room, lies at the bottom of this as a distinct layer or stratum, demonstra- ble by a thermometer, and forming a dangerous cold- bath for the feet of the inmates, often compelling deli- cate persons to keep their feet raised out of it by foot- stools, or to use unusual covering to protect them. 5. Bad ventilation.—Notwithstanding the rapid change of air in the room, perfect ventilation is not effected. The breath of the inmates does not tend towards the chimney, but directly to the ceiling; and as it must therefore again descend to come below the level of the mantel-piece be- fore it can reach the chimney, the same air maybe breathed over and over again. In a crowded room, with an open fire, the air is for this reason often highly impure. As another source of impure air in a house, it may be no- ticed that the demand of the chimneys, if not fully sup- plied by pure air from about the doors and windows, operates through any other apertures. 6. Smoke and dust.—These are often unavoidable from an open chimney, much affecting the comfort and health of the inhabitants of the house, and destroying the furni- ture. Householders would make great sacrifices in other respects to be free from the annoyance of smoke. In large mansions, with many fires lighted, if the doors and windows fit closely, and sufficiency of air for so many chimneys cannot therefore enter by them, not only do the unused chimneys become entrances for air, but often the longest and most heated of them in use overpower the shorter and less heated, and cause the 7 shorter chimneys to discharge their smoke into the room. 7. Loss of time.—During the time every morn- ing while the fires are being lighted, the rooms cannot be used; and there are, besides, the annoyances of smell, smoke, dust, and noise, all of which are again re- newed if the fire is allowed to go out and to be re- lighted in the course of the day. 8. Danger to person and to property.—How numer- ous are the losses of property by carelessness as to fires is well known to all, while the less frequent but more distressing loss of life too well attests the danger to chil- dren, and to females thinly clad, often consequent on an open fire. Such are the objections enumerated by Dr. Arnott, to which we may add, the annoyance and injury occa- sioned by the unavoidable ashes and dirt attending this mode of heating. Coal and kindling cannot be habitu- ally brought into a nice room without injury to the carpet, aside from the liability of sparks of fire to fall upon it. What careful hand can remove the ashes and cinders, or poke the fire, without setting afloat a storm of ash-flakes, which settle upon books, furniture, &c. ? The danger to human life by exposure to open fires, is too well attested by the fact that nearly every news- paper contains the sad account of death from this cause. We copy from a city paper two melancholy examples:— "Yesterday noon, Ellen Lynch, a child four years of age, r • t 4^ -7 Clark Street, was left by her parents in a room ^irll^rO. *. -t-n of her mother, the child with her httle «9ter- h aU her clolhes burned off, as with the grate." 8 "A child two and a half years of age, left to itself, attempted to climb up on the fender, for the purpose of taking something off the mantel-piece, and in doing so fell inside, between the fen der and the fire, and was thus roasted alive." STOVES. Next in the progress of improvement come the in- numerable patterns of stoves. With the exception that they can be cheaply bought, and are somewhat more economical of fuel, their use is attended with all the evils of the open fire-place and grate, with the ad- ditional objections of taking up valuable room, being unsightly, and, worst of all, they produce some of the evils of the hot-air furnaces in presenting a heating sur- face, the temperature of which is sufficiently high to kill the animalculse of the air, and scorch the myriad parti- cles of dust floating therein, rendering it unfit for res- piration, and so dry as to injure wood-work and fur- niture. The evaporating vessel of water on the stove is but a poor remedy for this evil. Stoves also come in competition with our lungs in the consumption of the oxygen of the *ir to support combustion, and do not recompense us for the loss, as in the ventilation which we get from an open fire. Stoves, when the heating surface is so far extended by long lengths of smoke-pipe or otherwise, as to take up and impart directly to the space to be warmed, all of the caloric set free by combustion, are, of all methods, the most economical of fuel. When stoves and open fires were first brought into use, it was through absolute necessity, instead of any merits which they chanced to possess. The latter came in vogue when wood was most abundant, and the fire-place was built capacious enough to serve the double purpose 9 of cooking and warming. We date back but a few yeara to the first use of the grate, and the substitution of coal for wood. Custom alone has familiarized us to the danger and inconvenience of these two methods of creating artificial heat. Should a stove, for instance, even of the most or- namental pattern, now be erected in our dwellings for the first time, its uncouth, black visage alone would be a matter of unendurable disgust. But when we take into account, above all things else, the thousands of human lives which statistics show are annually destroyed by exposure to open fires and stoves—children playing within reach of these fiery fiends—women drawn within their fatal circle—are we not led to believe that custom can habituate us to the most apparent and appalling of evils ? Here is a specimen of the old familiar story: Ann Clifton, died at her residence, No. 43 Laurens Street, from the effects of burns received on Sunday evening when her clothes took fire from a stove. Coroner's verdict, "Accidental death."—Sun, Jan. 24, 1860. HOT-AIR FURNACES. Of all potent inventions for the destruction of human life which custom has tolerated under the head of modern improvements," no one ranks higher than the modern i p ^ from them ^T^Z^oolaringly apparent, that we can arc »^ ' for their general mtroduc- oonceivc of no at* ^ ^ other ar. tion than tha^ they- ^ ^ ^ ^ rangements for warn ^ ^ ^ 10 of iniquity is still welcomed as a household companion because its first cost is small. When we take into con- sideration the great amount of fuel which they consume, the injury to wood-work and furniture, the high rates of insurance charged where they are used, the many valuable buildings they destroy by fire, and, above all, the invaluable human lives which are being daily sacri- ficed—burnt-offerings to this system—who can call them cheap, although their market value may be small? Men are wise in not employing them to yield warmth to the flowers and exotics of the green-house and con- servatory. But human plants—flowers of immortality —may sicken by inhaling their polluted breath, and wither away under the Sirocco-like blasts of this abom- inable system of heating. THEIR INJURY TO HEALTH. The fundamental evil of hot-air furnaces lies in the very limited amount of heating surface they contain. The air we are to breathe should never come in contact with surfaces sufficiently heated to char the innumerable, minute, dusty particles of decayed animal and vege- table matter always floating therein. 250° is the limit to which any surface should be heated. Or it should be kept at a temperature so low, thatj in ordinary cases, with the surface situated below, as hot-air fur- naces are, 1 square foot of heating surface would be re- quired (to give a sufficiency of heat in the coldest of weather) to every 100 cubic feet of space to be warmed. Take, for instance, a house containing eight rooms, aver- aging in size 16 feet square and 12 feet high=24,576 cubic feet of space to be warmed. This would require of heating surface, at a temperature of the above limit, 245 square feet; but a hot-air furnace of the size usu- 11 ally put in to heat such a house, would not exceed 75 square feet of heating surface. To make this small amount sufficient in cold weather, it is necessary to heat it to a temperature ranging from 800° to 1,000\ The baking temperature of an oven is 320°; wood will ig- nite at 350°; but what may be said of the healthful- ness of air heated against surfaces which exceed the burning point of wood by 650 degrees ! By excessive heating, the air itself is decomposed, its animalculse de- stroyed, and their innumerable dead carcasses—if we may so speak—are thrown into the apartments being heated. The effluvia of the decomposition of this mass of animal matter constitutes a part of the disagreeable odor which escapes from the registers. Air being al- most a perfect non-conductor of heat, one particle does not warm another; therefore the air which actually comes in contact with the over-heated furnace is the air by which we are warmed and which we inhale. The leakage of gases is a gigantic evil of this mode of heating, and is inseparably connected with it. A furnace cannot be cast whole, and consequently it must have joints, which, by the continual strain of heating and cooling (expanding and contracting), will invariably become broken—no matter how substantially they maybe put together with bolts,screws and cement. These joints come against the fire on the inside, and the air to be heated on the outside : consequently, whenever a joint is broken, the gas from the burning coal is drawn, by the greater current of the air rushing up- wards into the rooms that are being warmed. A furnace may keep « gas-tight" for a few weeks, or it may apportion out its gaseous poison ^ such Per- petual regularity as to inure the occupants of the house L an unconsciousness of its presence; but a compound 12 of carbonic oxide gas mingled with smoke and ash-dust, can be detected escaping from ninety-nine out of every hundred furnaces that are in operation, even by olfac- tory organs of ordinary ability. We were present, a few evenings since, at an evening meeting in a fashion- able Church (but too poor to permit pure air and health to its members), where two ladies fainted by reason of the above-named evil; and the entire audience, no doubt, were affected to the extent of a headache apiece, from the same cause. While thousands may be pining away by sure de- grees through this domestic iniquity, the public are only startled by an announcement like the following— the death of two highly valued citizens. We copy from the New York Times, of Jan. 17, 1860 : "Mr. and Mrs. Sawyer, of Haverhill, Mass., died in their bed, on Saturday, 7th inst., in consequence of breathing coal- gas which escaped from a newly-erected furnace. When Mr. and Mrs. Sawyer were discovered in the morning, artificial res- piration was unsuccessfully attempted as a means of restoring life. The air which escaped from their lungs was strongly im- pregnated with the gas which they had breathed." There is also an arsenical escape from the highly heated iron, which, too, has its poisonous influence upon the air we are to breathe. And this is what dealers in hot-air furnaces call " ventilation^—a trite term em- blazoned on their warehouses, as the surest decoy to catch purchasers. Danger from Fire.—Another evil of the hot-air fur- naces is their constant liability to fire the premises to which they are attached. The small quantity of fire- surface and heating-surface which they contain, renders it necessary to drive the fire to the highest point, in cold 13 weather, and in moderate weather, the lack of any reli- able control of the draft of the fire, with most of the heat shut back and concentrated at the furnace, engen- ders a dangerous heat, besides causing a wasteful con- sumption of fuel. These conditions, also, produce in the furnace and its surroundings a heat so intense as to open seams in the iron and brick-work, through which escape fire and combustible gases. Many furnaces are erected without " double tops," or any separation between the furnace and the ceiling di- rectly over it. Such arc condemned by all insurance companies, and are pre-eminently dangerous. Nor is the danger confined to the cellar. The hot-air flies from the furnace at a temperature high enough to ignite any combustible thing with which it may come in contact. The tin-conducting pipes serve as protectors so long as they retain their bright reflective surface; but the va- rious gases arising from the furnace, and the friction of the rapid current of air, soon change the bright, non- conducting surface of the pipes to dull conductors of heat, the solder will melt from the joints, crevices will be opened, and the contiguous wood-work set on fire. It has long since been ascertained that the continual action of heat will char tin and even burn it away. The pipes often become broken by the settling of the walls into which they are imbedded. It may with truth be said that it is hardly possible to erect a modern hot-air fur- nace without the liability of fire. Official investigation proves that two-thirds of the fires are traceable to this system of heating, and the fire insurance companies have been compelled to increase their rates where this kind of heater is used, while they offer a premium for safer modes. The unequal distribution of heat is an important 14 sanitary reason against the employment of hot-air fur naces in producing artificial warmth. The unnaturally heated air, rushing into the apartment with the velocity of a tornado, ascends at once to the ceiling, and, ren- dered specifically lighter than the air already in the room, it descends only as that may be displaced. The thermometer will, in a common room, indicate a differ- ence in temperature of 10° to 15° between the floor and ceiling. Hence the headaches, dizziness, cold feet, and the many indispositions to which the occupants of such rooms are continually subject. There are other causes and conditions which operate to prevent this highly ra- rified air from being equally apportioned in an apart- ment ; but were the air as pure as the element from which it was perverted, such inequality of distribution would be an unanswerable argument against the system. The same pieces of iron that form the fire-pot also heat the air from which warmth is derived, and these in the hot-air furnaces can only be located in one and the same place, and such locality must, of necessity, be at very unequal lateral distances from the rooms to be warmed, with the hot-air conducting pipes of correspond- ing lengths. Rarified air has a tendency only to ascend and is incapable of being forced any distance in a hori- zontal direction, except through the application of some mechanical force. It will naturally rise through the first openings, hence the rooms nearest the source of heat, (the furnace,) are unduly hot, while those more remote may not be warmed at all. But if at times the distant rooms should receive a flow of heat, there is no certainty of their being thus favored again, as the force of such is so feeble, that some capricious current of air in the house, or some " ill wind" without, is sure to affect it. We lay it down as a positive rule, that to insure warmth 15 to any space, the source of such warmth must invariably be located directly beneath or within it. Unequal heights, also, are unfavorable to the even dis- tribution of heat. One warm-air duct terminating at a higher point than another will have the greater flow of heat, on the same principle that a tall chimney will draw better than its shorter neighbor. In hot-air furnaces two conditions unavoidably exist to create this inequality in the upward currents. One is the unnatural lightness, and, consequently, buoyancy of the highly heated air; the other is the one hot-air chamber supplying all of the warm air ducts. So, in addition to our rule respecting the lateral conduction of warmed air, the same equality of condition must be maintained in its vertical distri- bution. They do not ventilate.—Although the force which the hot air rushing in exerts upon the air in the room may expel it through some apertures of egress, and thus effect a thorough change, yet this does not constitute ventilation in the true signification of the term. The air is made no better by the process, but rather worse. The comparatively pure air of the room is merely ex- changed for that which is contaminated. Their irregularity of fire.—Subject to the capricious discretion of domestics, and without any self-regulating contrivance to check excessive combustion, the fire is left to a wasteful and dangerous irregularity. When you require the least heat in your apartment, the ser- vant has considerately raked out the grate, opened the draft, and put on a surplus of coal; but, when you really want heat, the draft-damper happens to be closed, and the fire clogged, and, for all the servant knows, it is a mystery why the fire does not burn better. The closing of registers and excluding hot air from 16 the room, does not, as in the case of a well-construct- ed steam apparatus, have the effect to check the draft and deaden the fire, but rather to increase it, for the greater the heat against the furnace, the more the draft is accelerated and the hotter is the fire. With every means of escape closed, and a heavy fire raging, it may be readily seen that the air in the hot-air chamber and pipes leading therefrom would become dangerously hot; and, robbed of all its vitality, would, in this in- stance at least, become unfit for respiration. The evaporating pan.—The evaporation of water from a vessel placed within the enclosure of the furnace, is but a poor remedy for the scorching of the air. The excessive and irregular evaporation, which is unavoid- able, is frequently more objectionable than the over- dried air. The moisture is only mechanically taken up by the currents of air that may happen to come in contact with the water. This does not reinstate the original vitality of the atmosphere, nor recompense it for the loss of its natural moisture. Papered walls and furniture are often injured, and even ruined, by exces- sive humidity from this source ; and its effect upon our personal health is certainly a matter of serious moment. The visible deposit of vapor on the windows and walls in the kitchen, is an apposite example of the effects of excessive evaporation. Improved Combinations.—A great diversity of pat- terns, and many wonderful " scientific" and " philo- sophical" applications and " combinations" are displayed in each quarterly edition of this modus operandi for creating artificial heat. Some adopt an apologetic at- tachment in the shape of a few feet of steam or hot-water radiators; others vaunt themselves of some " self-cleaning " " gas-consuniing," or " super-heated " 17 paraphernalia, but they all amount to one and the same thing, and are subject to the same objections. We lay it down as an incontrovertible law, which will meet the approval of every candid mind that has given the subject a thought, that no apparatus is fit to create artificial warmth for human beings, vjhose air-warming surfaces are contiguous to the fire and its attendant gas, smoke, and dust. Remarks.—Such are a few of the many evils con- nected with the use of the modern hot-air furnace; and yet, because their first cost is small, they are more uni- versally used, in America, than any other heater that sends its heat up from below. But their employment is peculiarly an American institution. Intelligent for- eigners attribute our bad health and complexions to their use. It is to be sincerely hoped that as the public be- come enlightened on the subject of artificial warmth, and the laws of health relating thereto; and as less ob- jectionable modes of heating are brought within their reach, this unnatural arrangement will be consigned for- ever to oblivion. HOT-WATER FURNACES. For want of proper knowledge in the adaptation of steam for warming purposes, especially for domestic use, the hot-water, or more properly the warm-water ap- paratus has been resorted to by many as a remedy for the evils of the hot-air furnace. Their merits consist in their being directly opposite in all their features to the hot-air furnace; and their demerits are that these opposite features amount to ex- tremes. Their sins arc rather of omission than commission. The heat they yield—so far as it goes—is of an agreeable 18 and healthy kind. But the cold breath of winter does not agree with them, as the many inefficient members of this family now laid aside bear conclusive testimony. It has been properly styled " a warm-weather heater." The most approved patterns do, however, give heat enough except in very cold weather. The hot-water apparatus is not of modern origin; it has been more or less in use almost from time immemo- rial. Its ancient usage was confined more particularly to green-houses, graperies, &c, &c. In this department it possesses some decided virtues. The warming surface in this case (usually consisting of four-inch cast-iron pipes) is placed directly within the space to be warmed, extend- ing its entire length. The surface being ample, and the large body of water circulating freely through the pipes, an even temperature is maintained. This temperature can, by careful firing, with an ample supply of heating surface, be graduated to the requirements of most con- ditions of the external atmosphere. But this nicety of modification to any required temperature implies a skil- ful and ever-watchful gardener and fireman. For warming private residences the pipes are gener- ally smaller, and are located in the cellar, in the same position as the hot-air furnace. The air being but mod- erately heated, the pipes conducting it into the rooms are necessarily very large. The same necessity requires the heating surface to be very extensive, and consequent- ly to occupy a large space, and involves a heavy expense in its construction. Owing to a large body of water being heated, the apparatus is very slow in getting up its heat, but, as a partial recompense for this defect, it is equally slow in parting with it. Water is one of the best retainers or bottlers-up of heat, which fact argues against its effi- 19 ciency as a heating agent—at least against its rapidity of operation. Liability of freezing.—One of the most serious ob- jections against this mode of warming, is the constant lia- bility to freeze. So long as the wThole body of water in the pipes is kept in circulation, this cannot, of course, oc- cur. But the fire, which disturbs the equality of tem- perature in the water and causes it to circulate, is liable, through neglect or otherwise, to go out. Or if the fire be quite low, it may not cause a circulation, owing to the friction of water against the immense surface. The water always remaining in the pipes, and often remote from the fire—its exposedness to the out-door inclemency by means of a large cold-air box—the force with which the inward current impels it against the pipes—these circumstances combine to increase the liability of the water to congeal. There is usually a damper in the cold-air box by which the out-door cold may be excluded, but its adjust- ment depends upon the servant, who, if careless enough to neglect the fire, would certainly fail to attend to this. The high-pressure form of water furnace.—This is an arrangement whereby the heating pipes run through the house and are coiled directly within the various apartments to be warmed. It is the inven- tion of Mr. Perkins, formerly of Massachusetts, but now of London, England. It is now nearly obsolete in the United States, although it was once adopted here to a limited extent. Some of the apparatus of Mr Perkins are made to operate under a pressure of four thousand lbs. to the square inch. This plan possesses all th<.objec- tionable features of the other, with some additional ones. 20 Its liability to freeze is not as great, but the re- sults are more disastrous. Where the pipes run to any considerable height, the hydraulic pressure on the lower part of the apparatus is very great; this, with the amount of expansion and contraction by heating aud cooling of long lengths of pipe, creates a liability of leakage from the numerous joints, stop-valves, &c, which in nice rooms would be inadmissible. Such a large volume of water, extending, as it does, from cellar to garret, would, in a case of breakage, flood the house and furniture to their ruin. No ventilation is produced by this system ; and the coils in the rooms have to be covered by screens which take up valuable space and are not very ornamental. Inequality of temperature of ivarm-water heating surfaces.—As the water in the tubes may have a gradu- ation in its temperature, all the way from 32° the freez- ing point, to 212° the boiling point, it is impossible for it to maintain an effective heating surface against the ever-changing temperature of the out-door air which is drawn against it to be heated. We have in another place given a rule that the temperature of the surface against which air is to be warmed should hold the same against whatever change that air may be subject to, and the correctness of this rule we think must be obvious to all who have given the subject any thought. The cutting properties of an instrument become diminished as its edge is impaired; so with warm-water warming surfaces, the cold breath of winter blows over them, blunts their heating force—and a cold house and a cold day come to- gether. Water may be any where in the scale of tempera- ture from tepid or luke-warmth to boiling, and be warm or hot water still; while steam (as an opposite example) cannot exist at a lower temperature than 212°—a very 21 effectual heating point. Even with the heating surface abundant, and the fire in good condition, the cold air will lower the temperature of the pipes to a very inef- fectual point, and these conditions may be less favorable to an extent to admit of freezing, even while the water is travelling on its sluggish course. But steam apparatus with boilers properly proportioned to the heating pipes, keeps them fully supplied with steam, and the tempera- ture of the surfaces is not at all diminished, let the air that comes against them be as it may. He&t given off to no purpose.—Water being an ex- cellent retainer of heat, as indicated by the long time required after the fire is built to make the heat available, and, consequently, equally tardy in parting with it, there is a decided loss in warming school-houses, churches, stores, and all places where warmth is required only a limited portion of the time. For instance, a building requires warming but six hours out of the twenty-four; to do that with a water apparatus the fire must be built eight hours before the building is used. Now a good steam apparatus (a part of whose small body of water is converted into steam (212°) in a few minutes) is capable of warming the apartments sufficiently in two hours; consequently, it has but two hours to give off its heat to no account when the fire is allowed to go out, and warmth is not required; while water, with an excess of six hours in the commence- ment, has the same length of time (six hours) to waste its heat. This feature in the water apparatus, together with the lack of self-control to the fire, accounts for its extravagant consumption of fuel. Its principal merits consist in the opposite conditions to hot-air furnaces in respect to extent and temperature of the heating surfaces. oo The mongrel form of water furnace is a combination of surfaces heated by hot water, steam, and the fire itself. In some arrangements the last-named agent predomi- nates ; in others, the second. In one instance the air to be warmed, after passing over the red-hot surfaces of the hot-air part, is cooled or tempered against a meagre amount of water or steam surface; in another, it more properly passes first over the water surfaces, and after- wards over the steam surfaces. Another contrivance is sections of cast-iron hexag- onal-shaped flues,- stacked together directly over the fire. Within these flues are sometimes placed strips of thin sheet iron, with a view of conducting the heat more rapidly from the actual heating surfaces. This appa- ratus has a steam chamber, blow-off valve, etc., and would more properly come under the head of steam heating. The air is drawn simultaneously over steam and water surfaces, and then against the bricks by which the whole is enclosed. The air warmed by this process is mixed up with a deleterious compound of water-heat, steam- heat, and smoke, ashes, gas, and other poisonous resultants of leakages from the fire-pot and fire-chamber. This system, besides its similarity to the hot-air furnace in collecting within its heating compartments the residuums of ordinary combustion, possesses a more dangerous feature in its confined steam than any steam apparatus now before the public. But so long as it goes under the pacific cognomen of " hot-water furnace," its true character will not be generally understood. The evils of locating heating surfaces contiguous to the fire are most apparent. As we stated, in speaking of hot-air furnaces, the partition dividing the fire from the hot-air chamber will unavoidably become warped and broken. Whether they consist of brick, stone, or iron, 23 the continuous action and reaction of excessive heat will soon break the joinings sufficiently to allow the escapement of gas, smoke, and ashes from the fire, to find their way into the hot-air chamber. This evil exists to an inadmissible extent in nearly every heating apparatus yet erected, and is particularly flagrant in the above-named device. We think every in- telligent mind will coincide with us on this point—that even the liability of leakages from the fire into the air we are expected to breathe, should not exist. In point of durability, the water apparatus is de- fective when its heating surfaces consist of cast-iron tubes or sections. This is owing to the impracticability in foundries of casting even thickness in " core work." The adjustment of " cores " for a great number of pieces, especially if they are of considerable length, and have them maintain their positions during the process of cast- ing, may be laid down as one of the impossibilities of the trade. Even should the core remain in its place, the fused metal in the progress of pouring and cooling, must, from well known practical reasons, attain an ine- quality both in surface and ductility. Thus alternately thick and thin, soft and hard spots will occur in this species of foundry work. Tubes, or other cast-iron devices for heating pur- poses, are usually put together with cement, lead, cloth, India rubber packings, or some oxydizing preparations. Through the constant strain of heating and cooling, ex- panding and contracting, these joints will, sooner or later, become broken, or some of the more brittle por- tions of the surfaces themselves will crack, and leakage is the inevitable result. Miscellaneous objections.-*! using a large quantity of water, with no provision for drawing it off, sediment :M and mineral deposits will accumulate, and gradually im pair the efficiency of water-warming tubes. *. The very large amount of heating surface which they present to the air, is objectionable from the dust and refuse matter continually accumulating thereon. Hot-water operators find it impossible to keep the water just at its boiling and most available point, with- out its escaping in steam or overflowing; and the con- trol of the draft to the fire in conformity with the heat required, has not yet been accomplished by them. Experience does not prove that any form of hot- N water apparatus is other than wasteful in the consump- tion of fuel. LOW-PRESSURE STEAM-HEATING. It is acknowledged by all those who are acquainted with the nature of steam, that it is at once the most efficient, manageable, and economical of all agents for communicating and distributing artificial warmth. It occupies the same superiority of position in the heat- ing department that illuminating gas does in the de- partment of artificial light. Being of about the specific gravity of gas, and of an elastic and volatile nature, it is peculiarly calculated to flow to the desired point, even through long and circuituous sections of small pipes. It expands seventeen hundred fold over the bulk of water from which it is generated, and, in re- turning to water, imparts one thousand degrees of heat to the air, which in water and in an uncondensed state would be latent and unavailable. It admits of the most compact form, both as regards the space occupied for its generation, and the surface to heat the air. To construct a steam apparatus that shall be effi- cient, reliable in mechanical detail, and at the same time simple, substantial, economical, healthful, and perfectly safe, even in the hands of a common domestic—this is the great desideratum. COST OF CONSTRUCTION. A proper low-pressure steam apparatus cannot, if constructed of material of suitable durability, compete 26 in point of first expense, with hot-air furnaces, high steam, or any form of warming where a small amount of surface (by being over-heated) is rendered capable of warming a large amount of air. Where the temperature of the heating surface (which surface is the principal item of expense) is limited to a low and healthy quality, of course a larger quantity must be furnished than where the surface is heated to a much higher degree. The expense in the latter instance is materially lessened at the expense of health and safety. The same principle applies to the boiler that generates the steam. If it be stinted in size and of small capacity, it will require frequent attention, be extravagant in the con- sumption of fuel, and furnish an irregular and unreliable quantity of steam. But in comparison with hot-water, or any apparatus which has a superfluous amount of heating surface—surface whose temperature is unwar- rantably below the healthy point—the low-pressure plan can " under-bid "—the same space to be warmed, and all other things being equal. SAFETY FROM EXPLOSION To those not conversant with steam and its adapta- bility to domestic warming, the question naturally arises as to its safety when thus applied. The idea of " ex- plosion" is invariably associated with the mention of steam boilers. In every instance where an explosion has occurred, steam was confined under a very heavy pressure; a large quantity was in the boiler, and that, for want of water, in immediate contact with an im- mense red-hot generating surface, with a fierce fire raging at the same time. With a proper low-pressure 27 apparatus, there will be, at all times, a directly oppo- site condition of things. Instead of steam being under the pressure of 50, 75, or 100 lbs. per square inch, its highest possible pressure will not exceed one-tenth of the lowest of these figures, while every part of the apparatus is capable of sustaining a pressure of twice the amount of the highest figures. Instead of there being a million volumes of steam on hand at any time, one hundred would be the excess. Instead of the fire being driven to its highest pitch of intensity, (but low- est point of economy,) with a rapid draft, it burns very slowly, to a degree, and with a draft just sufficient to insure perfect and economical combustion. The supply of water to the boiler requires no more care and skill than does the tea-kettle on the range, and its neglect would involve no more disastrous results. But should a " bursting " happen at this low pressure, its consequences, compared with high steam, would be about as serious as the bursting of a pop-gun compared with that of a heavy piece of ordnance. Steam, in the proper form for warming purposes, is even less dangerous than gas. During five years of constant experience in applying steam to private dwell- ings for warming purposes, and out of some two hun- dred instances where steam has been thus applied, the author has not known of a single accident from ex- plosion, fire, or otherwise, where personal safety was at stake. Who can say as much of gas—not mentioning camphene, burning-fluid, and other dangerous sub- gtitutes ? SAFETY FROM FIRE. There is a prevalent ignorance on this subject, even among men whose official positions ought to lead them 28 to more extensive information. We will admit that Bteam has been known to set fire to buildings—water has done the same under like conditions. It is not the kind of apparatus, whether hot-air, hot-water, steam, or any other thing, that involves a dangerous condition from fire, but the quantity of caloric or heat which such apparatus or thing evolves. Ice, could it be heated to an equal temperature, would ignite whatever it came in contact with as readily as a red-hot iron bar. It is the temperature of the surface, let it be what it may, that implies danger from fire. That temperature, in the use of steam, generally depends upon the pressure which the pipes or radiators sustain, their thickness, the kind of material of which they are constructed, &c, &c. Yet pressure is not always necessary to produce high temperatures in steam. We have seen steam, under no pressure, and in the open air, ignite wood.* Steam, in its native and unconfined state, is a most effectual agent for extinguishing fire. The following table shows, in round numbers, the temperature of steam under different pressures :•— At the natural pressure of the atmosphere, boiling point, At lib. 5 lbs. pressure above do. 212° 212° 228° a 10 tt « u 241° tt tt 15 20 it it (The limit of» healthy temper-ature for any heating surface.) M (( 251° 260° It 25 tt it a 269° it 30 u a it 276° It 35 n it u 283° tt 40 it u it 289° it 45 u u a 295° * Super-heated or sur-chargetl steam. 29 At 50 lbs. pressure above 301° 55 « it a 306° 60 " a it 811° 65 " u it 315° 70 " Bread hakes and wood Morchea. 320° 75 " it a 324° 80 " a a 328° 85 « a a 332° 90 " a (i 335° 95 " a it 339° 100 " a ti 342° Thus it will be seen that the danger from fire in the use of steam depends altogether upon the temperature of the pipes in which it is confined, and that temperature (in common use) depends upon the amount of pressure of steam in those pipes. We can refer to a thousand instances where pipes containing low-pressure steam are run in every point of contact with wood, shavings, paper, and the most inflammable substances, and, after many years' use in such positions, they have not yet caused even " the smell of fire." The Board of Fire Insurance Companies of New York has recently decided this ques- tion in favor of low-pressure steam, and agrees to make a deduction of ten per cent, on all risks where it is ex- clusively employed for warming. SELF-REGULATION. This is the most important feature in the construc- tion of a proper warming apparatus. All of the most common artificial heaters of the present day are without any such arrangement, and are unable to have it, for want of some available mechanical force. Steam is pe- culiarly calculated to effect this object, as the small amount of power requisite is easily applied, by a very 30 simple mechanical contrivance, to shut off and reverse the draught to the fire, and to prevent any possible ac- cumulation of steam beyond the desired limit, even more perfectly than an intelligent being, constantly in attendance, could possibly do. It is evident that the fire should burn, and the fuel be consumed, only in proportion as heat is required. The quantity of heat thrown off from the heating sur- face depends upon the quantity of steam it condenses; and the extent of this condensation depends entirely upon the amount and temperature of the air coming in contact with the surface to be warmed. Thus, when a large amount of cold air is brought against the heating or radiating surface, the condensation is rapid, a large quantity of heat is evolved, the steam used fast, the pressure diminished, the draft opened, and the consump- tion of fuel increased. On the other hand, if the air to be warmed is taken against the surface at a higher tem- perature, and the amount diminished by its ingress being shut off from any room, the condensation is diminished, less steam is used, the pressure increased, the draft closed, and the fire checked to the requirements of the steam. By this arrangement, it will be seen that steam is the regulator of the fire that generates it. This is all-im- portant, as the fire is the prime mover, and no steam or heat can exist without it. On this feature depend safety, economy in fuel, general convenience and health- fulness. Without it no apparatus is complete, and no steam apparatus admissible. The mechanical construc- tion of such an arrangement must needs be of the most simple, substantial, and reliable kind, and proof against any contingency. 31 ECONOMY IN FUEL. By the perfect regulation and control of the draft, causing the fire to burn only as the demand for heat is required, and invariably closing when that demand is met; the water also from the condensed steam running back by its own gravity to the boiler, and constantly re- converted into steam, with only an incidental waste— and, consequently, not drawing upon the fire to heat cold water;—the proper construction of the boiler to insure the most perfect combustion, and the full absorption of the caloric of the fuel in the generation of steam—these are the principal conditions on which the consumption of fuel depend, and are all maintained in this apparatus to a degree of economy not equalled by any other. By practical experience, the author is convinced that in the use of a properly constructed low-pressure appa- ratus, under like circumstances, one-half less the amount of fuel will be consumed than by a common hot-air fur- nace, and nearly the same ratio will hold good in com- parison with hot-water and high-steam. LIABILITY TO FREEZE. This evil, which is such a serious one in the use of the hot-water apparatus, scarcely exists in this. Steam, of course,'cannot congeal, and the water resulting from the condensed steam, running back to the boiler through warm pipes, certainly will not. There is only one con- dition under which freezing can occur in the arrange- ment under consideration, viz., when the boiler is located in an exposed place, and the fire is permitted t0 be out for several days, the small amount of water m it may freeze, though this may happen without injury to the boiler. 32 The draft of air through the cold-air duct to the heating surface is regulated by a damper operated by the pressure of steam, and is proportionate to the 4] amount required to be heated—the same as described under the head of " Self-Regulation." Whenever the fire and steam go down, this damper is invariably closed, and the cold external air shut off from the heating surface. If but a part of the surface is filled , with steam, or the ingress of warmed air into the room is stopped by the closing of registers, a corresponding amount of air is admitted. Thus it will be seen that >j this arrangement not only secures an even temperature to the air warmed, but prevents the liability of freez- ing from this source. QUICKNESS OF OPERATION, AND STEADI- NESS OF HEAT. Having but a small quantity of water to heat, and a large fire-surface wherewith to heat it, steam is quickly generated and distributed through the heating surface. From fifteen to twenty minutes usually will suffice " to get up steam " and make the heat available. These causes also insure a steadiness of heat. By an ample fire-surface against a small body of water, the fuel is enabled, by burning at its very lowest point of combustion, to keep up the required head of steam; and this point is maintained by the control of the draft over the fire. Thus steam, and consequently heat, are kept 1 up so long as there is any fire. „•. In this particular it has been claimed that the hot- V « water-furnace is peculiarly meritorious, especially for green-houses, (though we do not admit that steadiness of heat, and equality of temperature, are more essential to the well-being of plants than they are to persons;) that 33 having a large body of water, it maintains its heat a long while after the fire goes out. This is true; but if it maintains it a long while after the fire goes out, it retains it equally long when the fire is first built. On the other hand, steam is generated with the kindling of the fire, and goes down when the fire goes out. In this respect we claim a superiority for steam, for it is usually most desirable to have heat when the fire is built, and to dispense with it whenever the fire burns away, or is extinguished. Both systems create heat equally while the fire is burning, but the difference is at the start and at the terminus. One withholds it from being available at first, to give it off leisurely after the other has ac- complished its duty. In the aggregate both systems evolve the same amount of heat under like conditions. The difference is only a matter of time. FREEDOM FROM NOISE. In the high-pressure form of heating, the noise oc- casioned by the collision of condensed water and steam being driven against each other, is very objectionable. The sound resembles the tapping of a hammer, and is continually kept up where long lengths of small lateral pipes are employed. In factories, workshops, and on steamboats, this noise may be admissible, but in private dwellings, schools, &c, never. Iron pipes, especially large ones, run to the different rooms of a dwelling, are objectionable in being such good conductors of sound The least rattle of coal or other noises at the boiler, can be heard quite as distinctly in some distant room as where it occurred. Neither of these undesirable features exists in this plan. The pipes are so arranged, and of sufficient size, and the pressure in them so slight, that 34 the flow of the steam upwards, and of water downwards, is free and noiseless. SIMPLICITY AND EASE OF MANAGEMENT. To have a heating apparatus—especially one that otherwise would be dangerous—simple and substantial in its construction, not liable to get out of repair, and entirely secure in the care of common domestics, is in- dispensably essential. This apparatus combines these necessary features. The fire requires to be fed, to keep up an even supply of heat, but twice in twenty-four hours. A fresh fire will seldom need to be built. There are no valves or dampers whose adjustment depends upon the care and judgment of any one. Only the simple and all-important items of fuel and water are required to be supplied. The supplying of these must, under any circumstances, rely upon human intelligence. No contrivance, though it be as perfect as mechanical skill can construct, is infallible, therefore none should be intrusted to fulfil this indispensable duty. The habit of the common domestic in the kitchen, of supplying with punctilious regularity, every morning, the water to the tea-kettle, and the fuel to the stove, amply qualifies her to attend to this duty—no more skill, judgment, or trouble is required in one case than in the other. The simple act of shutting off or letting on the heat, by turning the registers, whenever agreeable to the occupants of any part of the house, does, of itself, regu- late the fire, the accumulation of steam, and the amount of air to be warmed, as before explained. DURABILITY. Where a considerable expense, as well as some trouble is involved, we want, besides the assertion of 35 "for value received," an assurance that such is the case, and that what we buy will, besides appearing all right, be in reality of some lasting benefit. This is particularly desirable in a heating apparatus which is put into a private dwelling. Outside of the first cost, its erection is attended with more or less inconvenience and annoyance to the inmates. Some tearing away, altering and repairing of wood-work, brick, stone, &c, is also implied in the operation. The simple fact that this apparatus is capable, in all its parts, of sustaining a pressure of two^hundred pounds to every square inch, must be proof abundant and ap- parent of its durability. In short, the boiler, heating surface, and all the appurtenances connected, will last and hold good at least the average life-time of man. HIGH-PRESSURE STEAM-HEATING. We will briefly speak, by way of comparison, of a system of steam-heating which is directly opposite in all its features to the one we have been considering. Most persons have but a superficial knowledge of steam, and of course are ignorant of its different forms of application, both as an agent for heating purposes and as a motive power. All are familiar with the sight of the long lengths of small pipes running beneath the seats of steamboats, and around the ™™ / J^"1" and many other large buildings This is the high- pressure application of steam-heating, and has been in vogue for a great many years. The steam is generally supplied to these pipes from 36 the same boiler that furnishes steam to drive the engine, and they are subject to the same heavy pressure. This plan is a convenient one where a steam engine is re- quired, but the objections to it make it hardly admissi- ble under other circumstances. Disagreeable Noise.—The pipes, sustaining a high pressure, usually about fifty lbs. per square inch, and extending long distances in a level position, are liable to a constant noise resembling the tap of a hammer on the pipes. This disagreeable sound is caused by the steam coming in contact with the condensed water in the pipes, and which must be forced forward by the pressure of steam, as the horizontal position of the pipes will not admit of its running off by its own gravity. Health and Appearance.—The temperature of the pipes, under this pressure, is too high (300°) for a healthy and agreeable heat. The dust settles upon them and becomes burned, which, with the heating over and over again of the air of the room that is inhabited, occasion an offensive and unhealthy effluvia. The pipes are sometimes stacked up in short lengths, and covered with an iron screen, mounted by a marble slab. This is the customary mode in stores and hotels. The naked pipes, as well as the common clumsy pat- terns of screens, would have an objectionable appear- ance in private apartments. The Consumption of Fuel is much greater in a high pressure than in a low-pressure apparatus. Both philoso- phy and practice prove that in proportion as the pres- sure of steam is increased, the ratio of fuel required to give a certain amount of heat is increased, and vica versa. The sensible heat—the temperature of the heating surface—may be increased, while the latent heat—the great available principle in steam as a heat- 37 ing agent—is diminished. The amount of steam com- pressed in one instance, and the amount of steam con- densed in the other, are relied upon for heating power. Pressure involves fire, and fire fuel. The greater the pressure the less the quantity of available heat in proportion to the fuel consumed. In p$pof of this po- sition we would refer to two buildings in New York, in both of which steam is employed to warm about 700,- 000 cubic feet of space. In one, the apparatus never exceeded 2 lbs. pressure to the square inch, in the other the pressure ranged about 60 lbs. The amount of coal consumed during the same length of time (one season), with the other things being about equal, was one-half less in the low-pressure ap- paratus (70 tons) than the high-pressure (140 tons). We do not refer to this as a fair experimental example, as there were qualifying conditions, such as the more perfect regulation of the draft, &c, &c, in favor of the low-pressure apparatus; yet a fair test, under equally favorable circumstances, will prove the above compari- son nearly correct. Attention Required.—-The supply of water must be maintained by the use of a power-pump, to force the water into the boiler against the pressure of steam. The constant watchfulness of an engineer is demanded to attend to this, and to keep the fire fed with fuel The valves, also, in the different return-pipes of the boiler, need to be opened to ventilate the heatmg-pipes ot air, and shut when the air is out, to prevent the steam from ^Smtllness of JBoiler.-llero is a universal and most serious evil in the erection of the high-pressure appa- ratus The fire-surface being too small, the deficiency must"be made up in the intensity of the fire. With the 38 very strong draft necessary, the combustion is hurried, and consequently there is a large escape of partially consumed fuel up the chimney. But with boiler capacity sufficiently large to admit of slow and perfect combus- tion making the requisite amount of steam, the uncon- Bumed partiales, which in the other instance are lost, would be retained and burned, thus saving fuel, the labor of putting it on, and lessening danger. The intensity of the fire, and the rapid generation of Bteam, impair the boiler by throwing off the water from the fire-surface immediately contiguous to the fire, and exposing those parts, thus rendering them liable to burn. The smaller the boiler, the less the cost of construc- tion. The expense of the boiler is economized by the man who erects it, at the expense of the man who is obliged to furnish fuel for it. The danger of Explosion attending this Plan is owing, in a great measure, to the furious fire consequent upon the use of too small a boiler. A certain amount of steam is. required, and a small surface is, by being over- heated, taxed to its utmost capacity to furnish it. The fearful results of explosion are attributed to an explosive gas being generated by the throwing of water upon exposed red-hot surfaces, when the water becomes too low, and a large amount of dry, surcharged steam is packed and confined within a very small space. An ex- cess of pressure, merely, would cause a bursting at the weakest point, and the pressure thus being relieved, nothing more serious would result. The danger from fire by this system is explained in speaking on the same subject in connexion with the use of low-pressure steam, page 24. 39 SUMMARY REMARKS. There is at the present time a general dearth of good artificial heaters. Steam, as the agent for heating, is rapidly growing in public favor, and must eventually supersede all other modes, although it is, as yet, only in the incipient stages of development. The field is so broad and inviting that ambitious adventurers are plenty, each sanguine of ultimate success in attaining the much- desired object, viz., the construction of a cheap and. perfect steam apparatus. Most of them are entirely successful in obtaining the former quality, but fall lamentably below the standard in the latter. Many are the devices con- cocted within prolific brains to effect this object, and most as frequently is recorded the untimely birth of some alien to the legitimate household of heaters. Happily however, for the public, they seldom attain any further state of development. Steam for mechanical applications, and steam for warming purposes, do not go hand in hand. The offices of one disqualifies it for the proper duties of the other, and vice versa. Theory, practice, and philosophy, all agree on this point. Low pressure for warming—high pressure for mechanical force. Steam in its natural, uncompressed state, (212= the same as the highest temperature of water), imparts to the air a mild, healthy, and agreeable heat. Hot water does the same, but is less efficient, and liable to freeze. There is no danger from fire by either of these two modes High-pressure steam or water may be dangerous from fire because of the high temperature of its surface. By excessive pressure, they may have some of the unhealthy and dangerous qualities of the hot-air furnace. The limited amount of fire-surface and heating-sur- 4-0 face is a very serious deficiency in almost every heating apparatus of the present day. Where a small surface is required to do a large amount of warming, it must of necessity be heated to a very high temperature. This is done not only at the expense of fuel but of health. This evil grows out of competition in the trade to get up as cheap an article as possible. But many have found to their sorrow that an apparatus stinted in surface is the dearest one of all. The combustion is imperfect by be- ing too rapid, and a large quantity of fuel escapes and is wasted, which with a slower, fire would be burned. The fuel also has to be often replenished, and a de- cided loss of heat is incurred by the frequent opening of the furnace door, and the repeated kindling of fresh fuel. In hot-air furnaces the fire-surface is but the other side of the heating-surface—hence the intense heat that burns up the air, as well as the furna*e itself.* All heating apparatuses, especially those intended for domestic use, should have sufficient heating capacity to allow the fire to burn very gradually—so gradually that it need not, in ordinary weather, be replenished more than twice in twenty-four hours. It is very important to have the hall, which is the great artery of a house, properly warmed. On the tem- perature of this—extending as it generally does through all the stories—to a great extent depends the tempera- ture of the whole house. In fact, a house can be toler- ably warmed by steam, and at a very small expense, from the hall alone. VENTILATION. This is a subject on which a great deal of time, talent, and ink have been wasted. The acceptable meaning of * We have seen them so rotten a9 to literally crumble to pieces by their own weight. 41 the term is simply to keep the air of all artificial habita- tions in its natural condition—as pure as it exists in the broad expanse of space. To effect this object much labor has been spent, and many ingenious plans devised. Some have been successful to a certain extent, but most of them have failed of attaining the desired object, by being too complicated, expensive, &o. Impurities to which we are subject—The principal Bources of impurities from which in-door air requires to be freed by ventilation, may be briefly summed up as follows : 1. Expiration from the lungs of persons and animals. 2. Perspiration (sensible and insensible) from persons and animals. 3. Stoves of all kinds. 4. Hot-air furnaces. 5. Fumes and vapors from the kitchen. 6. Artificial illumination. 7. Unnatural dryness of the air. 8 Unnatural humidity of the air. 9 Evaporation from human and other bodies. 10. Decomposition of organic substances. 11 Stagnant air. 12 Damps of cellars and basements. iq