WAR DEPARTMENT, SURGEON GENERAL’S OFFICE, JUNE 4, 1870. 
REPORT TO THE SURGEON GENERAL 
OF THE UNITED STATES ARMY, ON THE 
OXY-CALCIUM L I G II T. 
AS APPLIED TO 
PHOTO-MICEOGEAPHY. 
By Brevet Lieut. Col. J. J. Woodward, Assistant Surgeon, IT. S. Army. 
Army Medical Museum, 
MicRosconcAL Section, 
BREVET MAJOR GENERAL J. K. BARNES, 
Jane 4, 1870. 
Surgeon General, U. S. Army. 
General: Since the preparation of my Report of January 4, 1870, on the use of the Magnesium 
and Electric lights in Photo-micrography, I have made some experiments with the Oxy-calcium, or Hare’s 
light, as a source of illumination for the same purpose, and have succeeded in obtaining excellent pictures 
with powers as high as a thousand diameters. This result appears to me of considerable importance, both 
because of the comparative cheapness of this light, and because the apparatus for its production is so 
common as to be practically within the reach of every microscopist. In addition to these advantages the 
Oxy-calcium light possesses the quality of steadiness to a greater degree than either the Electric or the 
Magnesium lamp and requires much less trouble and skill to manage. 
For the purposes of my experiments, I made the hydrogen as I consumed it, in a Hare’s self-regulating 
generator, by the action of dilute sulphuric acid on scraps of ordinary sheet-zinc. The oxygen was some- 
times made in the usual way from chlorate of potassa, sometimes purchased compressed in iron cylinders; 
in either case it was transferred to a large sheet-iron gasometer for use. The gasses were burned under a 
pressure equal to a column of water fourteen inches high. I used for lamp one of the first-class magic- 
lanterns, manufactured by J. W. Queen & Co., (No. 924, Chestnut Street, Philadelphia, Pennsylvania,) in 
which the disc of lime is revolved by clock-work before the burning jet of gas and a fresh surface con- 
stantly presented to the flame. I simply removed from the lautern the lens intended to magnify the image 
on the slides, when the apparatus is in ordinary use, and allowed the cone of light proceeding from the 
large condenser of the instrument to fall upon the achromatic condenser of the microscope, in the same 
manner as described and figured for the Magnesium lamp in my report of January 4th, a reference to 
which will render any description of the arrangement of the microscope and of the sensitive plate unnec- 
essary in this place. I employed tlie ammonio-sulphate cell, as I do in taking Photo-micrographs with other sources of 
light, but found I could dispense with the ground glass which is necessary in photographing so many 
objects, if sunlight or the Electric lamp is employed; a large portion of the lime-disc being luminous, the 
resulting mixed divergent pencil, like that obtained from the Magnesium lamp, does not produce the 
interference phenomena which result when the tissues and many other objects are illuminated by powerful 
parallel rays. This circumstance, however, renders the Calcium light inferior to the sun and the Electric 
lamp, in the resolution of the Nobert’s plate and certain lined test objects. 
I did not find the time of exposure differed materially from what I had given in making photographs 
of the same objects with the Magnesium lamp, and the pictures produced were not inferior to these in 
quality. This arose from the fact that the greater steadiness of the Calcium light permitted the use of 
condensers which concentrated the light to a greater degree than I had found advantageous with the 
Magnesium lamp, and not from equality in the actinic power of the two sources of illumination. I 
have recently made some experiments with the view of obtaining positive information with regard to the 
comparative actiuic energy of the Electric, Magnesium and Calcium lamps which I employ. Eor this 
purpose all condensers being removed the divergent pencil proceeding from each lamp in turn was per- 
mitted to fall, for the space of five seconds, on an exposed circular portion of a sensitive plate thirty feet 
distant. The whole operation was completed in less than a minute, when the plate being developed in the 
ordinary way three circular spots appeared as the results of the exposures. The spot produced by the 
Electric light was intensely black, that by the Magnesium of a rich middle-tint, while the circle impressed 
by the Calcium light was extremely pale. Want of time prevented me from continuing these experiments 
and obtaining as I desired numerical values for the relative actinic powers of these sources of illumination 
under definite conditions; this I have however regretted the less, as the actual energy of the naked flames is 
not really the measure of their availability in Photo-micrography; here the question of steadiness, involv- 
ing, as it does, the possibility of great concentration, plays a most important part and materially modifies 
the result. 
So far as I know, the Calcium light has never before been successfully employed as the source of 
illumination for making Photo-micrographs in this country. My friend Dr. 11. L. Maddox, however, writes 
me that it has been experimented with in England by Drs. Abercrombie and Wilson. He thinks they 
used powers as high as an eighth with pleasing results. This information has directed my attention to the 
essay of Dr. Wilson in the Popular Science Review for 1867, volume VI., page 54, in which that gentle- 
man gives in detail the process employed by himself and Dr. Abercrombie, lie experimented with an oil 
lamp and with the Oxy-calcium and Magnesium lights. He says, page 59, of the Oxy-calcium light: “I 
can scarcely think it would be used now that the more active light of Magnesium is within the reach of 
everyone.” And of the Magnesium: “The light fails only in steadiness, and if some means could be 
devised for burning the metal uniformly and at a fixed point nothing would be left to desire.” Dr. Beale 
(How to work with the Microscope. 4th Edition, p. 248) tells us that some of the pictures of these gen- 
tlemen were remarkably good, “they possess a peculiar delicacy in the half tones and the shadows, with 
much roundness of the objects, but the definition, as might be expected, does not quite equal in some of 
the finest markings, prints obtained from sun negatives.” A perusal of Dr. Wilsou’s paper will show that 
my process differs from his in the use of the following precautions: the interpolation of an ammonio- 
sulphate cell to exclude the non-actinic rays, the use of lenses specially made for photography for all 
powers from the ith down, the use of much larger condensers to concentrate the light and so to shorten 
the exposure, and in the case of the Magnesium light, in the use of a clock-work lamp to increase the 
steadiness of the illumination. Each of these points are in my judgment essential to obtain the best results. 
I learn from the same letter of Dr. Maddox that he had himself made experiments with the Mag- 
nesium lamp some time before those of Abercrombie and Wilson. He used powers as high as a fifth, and 
appears to have obtained better results than I supposed any one had done prior to the publication of my 
report. He gives me the following account of his experience: “The first picture I took with the Mag- 
nesium light was done in a very rude way. An inch and a quarter of wire was held in a small spirit flame and advanced by hand as burnt. The objective was Beck’s Ids, the object the sycamore-leaf insect, and 
about fths of an inch of wire remained after use. I sent a print, with a sun print of the same to the 
British Journal of Photography, and in the number for July 1, 1864, you will find some remarks by 
myself and the Editors. Now to try and meet any error that might arise from wdiat we may term want of 
correction, I used the Ids with the correcting lens, which is excellent for sunlight; the picture was soft, 
full of half tone, but wanted, as in other pictures I had seen by artificial light, the decision of definition 
in the outlines.” “After this I used the l-5th with the little apparatus sketched in Beale’s book (page 275) 
and which I venture to think, embraces all that is required for its use, provided the condenser has its focus 
at the burning point, and that the reflector has the same.” “With the 1 -5 th, fibres of cotton and muscular 
fibrillae of boiled shrimp, with several other objects were taken, but I did not use any higher power, nor 
indeed pay much attention to the subject as I gave the preference to the sunlighted prints and negatives.” 
I give these extracts with great pleasure, as showing the experience in this direction of one of the most 
distinguished laborers in the field of Photo-micrography, and regret that I was not acquainted with them 
at the time of publishing my first report. The method of Dr. Maddox, however, differed from mine in the 
same essential points as that of Abercrombie and Wilson, and the peculiar fitness of the Magnesium light 
for photographing the animal tissues and those objects generally, which require the use of ground glass 
when sunlight is employed, would appear to have escaped the observation of these accomplished gentlemen, 
and to have remained unnoted until the publication of my report. 
In conclusion I append to this paper two illustrative photographs. The first, which represents the 
6th square of the Moilers type-plate of the diatomaceae, taken with Wales’s 1>} inch objective, arranged to 
give thirty-five diameters, will serve for comparison with the photographs of the same object with the same 
lens taken by Sunlight and by the Electric and Magnesium lamps, which were published with my former 
report. The second represents the Navicula Lyra, taken with the Powell and Lealand s immersion 1-16tli 
arranged to magnify 1000 diameters. 
I have the honor to be, General, 
Very respectfully, 
Your obedient servant, 
J. J. WOODWARD, 
Assistant Surgeon and Brevet Lieutenant Colonel, U. S. Army, 
In charge of the Medical and Microscopical Sections of the Army Medical Museum. WAR DEPARTMENT, 
Surgeon General’s Office, Army Medical Museum. 
The Sixth Square of a Holler’s 
TYPE-PLATE OF THE DIATOMACEJE. 
Specially arranged for the Museum. 
Magnified 35 diameters by Wales’ inch and a half objective. 
Photo-Micrographic Negative No. 196. New Series. 
Taken by the Calcium Light. 
By Brevet Lieutenant Colonel J. J. WOODWARD, Asst. Surg., U. S. A. 
By ORDER OF THE SURGEON GENERAL. WAR DEPARTMENT, 
Surgeon General’s Office, Army Medical Museum. 
NAVICULA LYRA. 
Magnified 1000 diameters by Powell & Lealand’s immersion one-sixteenth objective. 
Photo-Micrographic Negative No. 219. New Series. 
Taken by the Calcium Light. 
Ey Brevet Lieutenant Colonel J. J. WOODWARD, Asst. Surg., U. S. A. 
By order of the Surgeon General.