696 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
makers are now making Microscope-stands with a series of draw-tubes, 
which enable one to vary the tube-length from something less than the 
Continental to something greater than the English length of tube, it is 
possible so to arrange the apparatus as to work at any length that 
seems to give the best results. 
If a large amount of difficult high power work is contemplated there 
cannot be the slightest doubt that it is true economy to buy the very 
best objectives that can be procured. And it may here be stated 
generally that objectives having as high an angular aperture as 
possible, and, in fact, giving the best possible image when used in 
the ordinary manner, will be found best adapted for photographic 
work. 
A form of apparatus that Mr. Kent has largely used, consists of the 
following parts : — A bracket is fixed upon a wall just below an aperture 
through which light enters. Upon the bracket the Microscope is supported 
in a vertical position, and the entering light is thrown upwards and 
through the Microscope by means of a mirror. Immediately above the 
bracket is fitted a support for the photographic plate, and this support 
can be placed nearer to or farther from the Microscope as a less or 
greater amplification is desired. Around the whole of the Microscope 
and bracket an opaque cloth is arranged to prevent the light entering 
by the aperture in the wall from escaping into the room. The eye- 
piece of the Microscope projects through a hole in the cloth. The plate 
support is provided with three points upon which the plate rests. Thus, 
there is no possibility of want of register between the focusing plate 
and sensitive surface as in the camera slide. Exposure is effected by 
means of a plate of ruby glass. The focusing is accomplished by 
placing the focusing screen upon the three points of the plate-holder. 
A general idea of the image is gained by using an unexposed gelatino- 
bromide plate as a focusing screen, and the final touches ^are given by 
replacing this with a piece of plate glass, and examining the image upon 
it by means of a double convex lens of long focus, or what does equally 
well, the field lens from an ordinary eye-piece of low power. All adjust- 
ments of the fine focusing screw are made through opaque cloth 
with ease. In an apparatus of this kind one is working inside the 
camera, and it is essential that all white light shall be excluded. 
The apparatus is equally well adapted for photographing either wet or 
dry preparations ; and while admitting that for constant work with the 
highest powers and dry specimens, one of the horizontal forms of 
apparatus would probably prove more satisfactory, yet for doing work 
which is only taken up at intervals, and where the Microscope cannot 
be devoted exclusively to photomicrography, it will be found an arrange- 
ment possessing many advantages. 
Whatever the form of apparatus decided upon, an efficient form of 
illuminant is a necessity ; and while many good workers prefer still to 
use the common paraffin lamp, perhaps the best illuminant for all-round 
work is the oxy-hydrogen limelight, and particularly that form of the 
light in which the gases are mixed before ignition. In this form of 
illuminating apparatus an extremely small point of very high brilliancy 
is obtained, and the diffusion of brilliancy observable in the blow- 
through form of jet is absent. With proper care it is quite possible 
