JOURNAL 
OF THE 
ROYAL MICROSCOPICAL SOCIETY. 
JUNE 1892. 
TRANSACTIONS OF THE SOCIETY. 
YI. — On a Series of Lantern Slides: Photomicrographs and Photo- 
graphs of Photomicrographic Apparattis. 
By A. Clifford Mercer, M.D., F.R.M.S. 
( Exhibited 16 th March, 1892.) 
Plate IV. 
Of the seventy-three slides exhibited, a few only will receive attention 
in this paper. These will be considered under the three headings of 
Photomicrographs of Natural Objects, Photomicrographs of Printed 
and Written Matters, and Photographs of Photomicrographic Appa- 
ratus. Before considering particular slides it may be wise to say a 
few words of a general character about the objectives and illumination. 
The objectives used were a 1/25-in. by H. R. Spencer, various 
objectives by Powell and Lealand, a 1/8-in., and a l|-in. by W. Wales. 
In no instance was an apochromatic used, and in only one instance an 
eye-piece. The Spencer 1 /25-in. is peculiar in having a collar adjust- 
ment for water, glycerin, and homogeneous immersion, with or with- 
out a cover-glass. The Wales objectives are corrected spherically for 
the violet ray. The violet image is therefore somewhat superior to 
the visual, with which, however, it is coincident ; and the fields of 
these photo-objectives * are unusually flat. 
The light, with two exceptions, was from the edge of a lamp- 
EXPLANATION OF PLATE IV. 
Fig. 1. — The spear-shaped ends of hairs from the “ carpet-bug.” 
„ 2. — A portion of a cricket’s tongue. 
„ 3 — Sphagnum leaves. 
„ 4. — A folded wing from a marsh-fly. 
„ 5. — A fragment of a Podura scale. 
„ 6. — A rent in a Podura scale. 
„ 7. — A folded Podura scale. 
„ 8. — A letter J from a forgery. 
„ 9. — A promissory note. 
„ 10. — The letter a in “ bearer ” of the promissory note. 
* Trans. Roy. Micr. Soc., n.s., xv. (1867) p. 254 ; and Monthly Microscopical 
Journal, vi. (1871) p. 172. 
1892. 
Z 
