MICROSCOPY. 381 
time he patented his well known objectives with two backs; one 
back being calculated to give a result of perfect correction for 
color, this being required by many microscopists, and being desir- 
able for many kinds of work; and the other back having the lens 
slightly undercorrected for color, for better performance in pho- 
tography and in extreme resolution by oblique light. It was, and 
is, claimed by Mr. Wales that such combinations furnish to micro- 
scopists a really valuable choice of qualities and of working power 
in objectives. 
Stupents’ Microscopes. — Since the publication in this Journal 
of a paper on the above subject, J. W. Queen & Co. have greatly 
improved their model of students’ microscope, availing themselves 
liberally of the modern suggestions on the subject. They have 
so introduced, under the name of Popular Microscope, a simpli- 
fied and cheapened form which seems fully equal to the old style 
of students’ stand. Experienced microscopists will be the first to 
appreciate the efforts of manufacturers to furnish really good in- 
struments at a price which will render them popular and thereby 
extensively useful. 
A New Ocurar Micromerer. — Dr. Pigott advises that the 
lines of an eye-piece micrometer be engraved on a plano-convex 
lens of long focus, such as a spectacle glass. As he explains that 
the convexity is too slight to appreciably alter the effect of the 
ocular, this form can only excel in ease of obtaining accuracy of 
workmanship, as compared with the commonly used contrivance 
of a stage micrometer cut down to such size as to lie in the focus 
of the eye-lens. 
Bioop-pisks or THE SaLMon.— Mr. George Gulliver called the 
attention of the East Kent Natural History Society to the preém- - 
inent size among osseous fishes, of red corpuscles of the blood of 
the salmon family, those of Salmo Jontinalis having a mean length 
of 45s inches and breadth of zzisg inches. On account of this 
peculiarity of size, “ Science Gossip” aptly suggests the choice of 
this blood to novices in microscopy who desire to study the blood 
of fishes, 
Tur Hicuesr Power. — Messrs. Powell & Lealand have com- 
Pleted and exhibited a one-eightieth inch objective which has an 
angular aperture of 160°, works through glass covers .003 thick, 
