190 J.J. Woodward on Photo-micrography. 
York. Besides these, mention must be made of the paper of Dr. 
John Dean of Boston on the Spinal Cord, which is illustrated by 
photomicrographs reproduced by photolithography. The work 
of D n however was done with magnifying powers not ex- 
ceeding ten or twelve diameters, while both Professor Rood and 
Mr. Rutherfurd have experimented with very high powers. 
Prof. Rood published a very interesting account of his process 
in this Journal in 1861.’ Omitting details, it appears from this 
paper that in his operations, he used direct sunlight for illumina- 
tion, and employed ordinary achromatic objectives with or without 
eye-pieces. The difference between the visual and chemical foci 
he endeavored to overcome by an alteration of the fine adjustment 
after the plan suggested by Shadbolt.? Prof. Rood thus obtain- 
achromatic objectives. In May, 1865, Mr. Lewis M. Rutherfurd, 
New York, published a paper on Astronomical Photography,’ 
which contained the following suggestive passages. “T 
vergence. On applying this test I found that an objective of flint 
and crown in which the visual was united with the photographic 
focus, (in other words, where the instrument sala be focalized 
on a plate of ground glass by the eye, as in ordinary cameras, 
and in the heliographs constructed by Dalmayer for the Kew 
observatory and for the Russian government,) is a mere com- 
romise to convenience in which both visual and actinic qual- 
ities are sacrificed. ” 
* On the practical application of Photography to the microscope; by Prof. 0. N. 
Rood ; vol, xxxii, p. 186 
. 
On the photographi ‘delineation of microscopic objects by artificial illumination. 
. of Mi i ci 
4. 
phic 
Geo. Shadbolt, Esq. Quarterly Journ. of Microscopical Science, xol. i, p. 165. 
Astronomical Photography ; by Lewis M. Rutherfurd, this Journal, xxxix, 30 
