74 Our Present Medical and Students' Microscopes. 
used by Dr. J. J. Higgins, of New York,* to whom I hasten to give 
the credit due. 
I am very glad to find Dr. Ward indicates the feasibility of 
the substitution of magnifying powers at a fixed distance as names 
for objectives instead of alleged equivalent focal lengths. I must, 
however, differ from him when he recommends that the distance 
should be measured from some part of the objective to the screen, 
instead of from the micrometer to the screen ; for however desirable 
this may be made to appear, it is not feasible. Nor can I agree 
with him in regarding 10 inches distance as having anything 
special to recommend it. To the question he asks at the conclusion 
of his paper, “ at what point of the screw-collar adjustment shall 
the objective be placed for rating its angular aperture and ampli- 
fying power ? ” I reply without hesitation, that for each purpose 
accuracy demands that the maximum should be given as well as the 
minimum ; that the maker should state not merely one limit, but 
both. 
Dr. Ward’s paper also contains some interesting suggestions on 
the subject of the nomenclature of eye-pieces, a matter which will, 
however, I think, particularly in the case of the ordinary eye-piece, 
require further discussion. I agree fully with Doctor Ward that 
eye-pieces should be named by their magnifying power : but the 
question at once arises, how shall this be accurately measured ? To 
this subject I may recur at some future time. — Sillimans Journal, 
June. 
IV . — Our Present Medical and Students' Microscopes. 
By R. H. Ward, M.D. 
Those who use the microscope as an elegant and costly luxury 
will, of course, be guided in so doing by their general ideas of taste, 
economy, &c. ; the few who use the instrument as medical experts, 
or original investigators in science, will, at the same time, by years 
of practice, grow into the use and the possession of an instrument 
suited to their wants ; but a larger class are those who use the in- 
strument as an incidental though frequent aid in their daily work 
in various sciences or professions, who reasonably desire the simplest 
instruments consistent with real usefulness, and who, however 
eminent in other specialities, are often unfamiliar with the styles 
and prices of the various makers, and at a loss to know what avail- 
able resources would best supply their wants. The following Tables 
are designed to be of use to buyers of microscopes, of the latter 
* ‘ American Naturalist,’ Dec. 1870, p. G28. 
