516 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
wheel without tire. The upper triangle of the four within the square falls 
away as useless ; the lateral triangles open outwards, and stand at right 
angles with the plane of the circle ; the little flanges on their lower edges 
are made by creasing the paper to support the thin glass. The base of the 
lower triangle answers the same purpose. 
“ Put the eye-piece in the Microscope, the circle of paper to the end of it ; 
turn the spokes of the wheel back along the tube, and slip a tiny elastic 
band over them, or tie them with a thread ; a little manipulation with the 
fingers, the thin glass is in place, and the thing is done. 
“ Need I say that any one can see that it would be almost as easy to use a piece 
of thin sheet brass or other metal as to use paper ? ”] 
Journ. of Microscopy, III. (1890) pp. 40-1 (1 fig.). 
C4) Photomicrography. 
Some Experiences in Photomicrography.* — “More than a dozen years 
have now elapsed since I made my first photomicrograph ; at that time 
the successful workers in this country could be counted on one’s fingers, 
and the old messy wet process and expensive appliances were regarded 
as indispensable for good results. The development of amateur photo- 
graphy following the general introduction of dry plates could not fail to 
influence photomicrography, since few microscopists viewed with indif- 
ference the placing at their doors of a ready means of recording observa- 
tions. The experience gained during ten years of continuous work, 
covering almost every class of subjects, with amplifications ranging from 
four to four thousand diameters, has, naturally, emphasized many facts; 
the possibility that a brief statement of these conclusions may aid 
younger workers in this field must be my apology for the egotism of 
these remarks. 
While appreciating fully and endorsing heartily the efforts of those 
working with no greater responsibility than their individual enjoyment, 
it is rather to those seriously engaged in endeavouring to produce the 
best and highest class of this work, that these suggestions are offered. 
The three essential conditions for success in photomicrography 
are: — (1) Satisfactory apparatus; (2) Good illumination; (3) Suitable 
preparations. 
Satisfactory apparatus by no means implies elegant appliances, but 
adaptation to purpose ; so that the Microscope be very solid and firm, 
and supplied with a substage to which a condenser can be attached and 
satisfactorily adjusted, and that the camera be of sufficient length, it 
matters little as to exact form or detail ; for high powers the mechanical 
stage is a convenience, and for extreme amplifications (2000 and over) 
well nigh a necessity. The most complete photomicrographical outfit 
to be had is, undoubtedly, the one made by Zeiss, of Jena. ... Of 
greater importance, however, is the quality of the objectives, for only 
those of the most perfect correction will stand the severe test of photo- 
graphy. While there are many others, which personal use has shown 
to answer well, my experience would lead me to select the following as 
being especially satisfactory: — 3 in. Crouch, 1^ in. Beck, 3/4 in. Bausch 
and Lomb, 4/10 in. (BB) Zeiss, 1/4 in. “Photographical” Bausch and 
Lomb, 1/6 in. (DD) Zeiss, 1/12 in. oil-immersion apochromatic Zeiss. 
The 3 in. Crouch and the 4/10 in. (BB) Zeiss deserve especial mention, 
* By George A. Piersol, M.D., of Philadelphia. Amer. Annual of Photography, 
1890. 
