BROOKES, ON MICROSCOPES IN THE EXHIBITION. 93 
render such binocular vision extremely irksome, especially if long 
continued. The construction is now so universally adopted in 
new instruments, and adapted to old ones, by all the leading 
British makers, that it would have involved needless repetition to 
mention it in each particular case. 
It would be unjust to conclude these observatiens without 
a commendatory remark on the extreme not less than unusual 
liberality, that induced Mr. Wenham to disclaim any personal 
pecuniary advantage from this most ingenious and useful in- 
vention. 
J. Casarteii, Manchester (2873). 
CuapBurn Brorunrs, Sheffield H.M. (2805). 
Ex.iorr Broruers, M. (2897). 
W. J. Satmon (2953). 
ER. G. Woon (2994). 
Microscopes are exhibited by all these firms, but none of them 
require special notice. 
Foreign Exhibitors, 
E. F. Harrnacr, Paris, M. (France, 1417), exhibits a fine 
collection of microscopes, the stades of which are generally on 
the Oberhauser model, in which the body of the microscope 
stands up from a heavy, hollow, cylindrical base or pedestal, the 
upper surface of which forms the stage. The bulk of these in- 
struments is much less than that of the first-class English 
microscopes; this is not probably attended by any disadvantage, 
except that, to a considerable extent, magnifying power is con- 
veniently augmented by length of body. The powers generally are 
very good—unquestionably the best in the foreign department ; the 
deepest is 1 millimétre focal length, and hence about equivalent in 
magnifying power to the 3;th of Powell and Lealand; but in 
penetrating and defining power it is, not comparable with that 
unique objective. 
Several of the deeper powers by this and other foreign artists 
are corrected for the transmission of the rays from the object to the 
objective, through some intervening fluid medium, as distilled water. 
This principle of construction has not been at all carried out in this 
country ; all our objectives being corrected for the reception 0% 
rays from air; it may, perhaps, possess advantages that are not at 
first sight apparent, and deserves more attention than it has 
has hitherto received. 
A. Mrranp, Sen., Paris (France, 1418), exhibit miscroscopes, 
the stands of which are after the ordinary English model. ‘The 
objectives are after the usual French plan, consisting of three 
similar achromatic lenses, superposed, which are either taken at 
random from a pile, or at best, matched by trial. This principle 
of construction is manifestly inferior to that universally adopted 
in this country, especially in all the higher powers, in which the 
