252 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
that, for the time being at least, it is the form adopted for storing the 
several thousand slides forming the Museum collections. 
I have attempted to show the arrangement as above described in the 
accompanying drawing. In reality the slides are held much more firmly 
than indicated, since the paper bulges and comes against both the front 
and back of the slides, the full length of the fold, instead of merely at 
the bottom. It will very likely strike the reader that a better material 
than paper might be found. I can only state that after considerable 
experimenting the paper was, all things considered, found most satis- 
factory.” 
C4) Photomicrography. 
Photomicrography and direct positive Enlargements.* — M. Fabre- 
Domergue points out the limits to the use of photomicrography as a help 
to the Microscopist, and shows what advantages a careful drawing made 
by means of the camera lucida possesses over a photomicrogram ; for 
while the artist in drawing superposes all the planes which he observes 
by means of successive focusing, the photomicrogram on the contrary 
only reproduces one of these, viz. that one which was in focus before the 
exposure of the plate. At present he considers that the questions 
whether the employment of photography considered as an auxiliary is 
really useful, and whether time and precision are gained by replacing 
the camera lucida by the photographic objective, would generally 
be answered in the negative. He ascribes the discredit into which 
photomicrography has fallen partly to the reason above stated and 
partly to the complicated apparatus required. Photomicrography can 
only be considered as a good method of work if it surpasses that of the 
camera lucida in rapidity, precision, and convenience, and these qualities 
he has not met with when he wished to make use of the complicated 
combination of apparatus now in vogue. 
For this reason he has returned to Moitessier’s original system and 
has made use of a small camera adapted directly to the Microscope, 
which gives small but perfectly clear images. The small proofs thus 
obtained are then enlarged by some of the new processes which have 
been lately considerably simplified. 
The process which the author advocates therefore consists in the 
application of new and improved photographic processes to an old 
method of operation which had fallen into disuse, and of which the only 
fault consisted in giving proofs too small to be directly used. 
He first describes the mode of operation for obtaining the small 
negative, and secondly the method of enlargement to a positive proof. 
(1) Taking the small negative . — The camera, which is entirely of 
wood, consists of a small box pierced below by an aperture, into which 
fits the body-tube of the Microscope, and closed above by a velvet 
cover. A shutter of cardboard, containing either a sensitive plate 4 in. 
by 4 in. or a ground glass, slides in a groove in the base of the box. 
The ground glass, on which two diagonal lines are scratched, is provided 
at its centre with a small disc of thin glass cemented to the plate by 
Canada balsam. Since the refractive index of the balsam is nearly the 
same as that of the glass, a transparent window is thus formed, by means 
* Ann. dc Microgr., iv. (1892) pp. 288-99, 569-75. , 
