64 On the Oxy-caleium Light, pel sen on 
I1.— Further Remarks on the Oxy-caleium Light, as applied to 
Photo-micrography. By Brevet Lieut.-Col. J. J. Woopwarp, 
Assistant-Surgeon, U. 8. Army. 
Stnce 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 hght, 
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 sometimes 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 gases 
were burned under a pressure equal to a column of water 14 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 
constantly presented to the flame. I simply removed from the 
lantern 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 unneces- 
sary in this place. 
I employed the 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-dise being luminous, the resulting mixed diver- 
gent 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. 
* €Monthly Microscopical Journal,’ June. 
