1864. | Microscopical Science. 135 
may be dispensed with, except in travelling, and the instrument, with 
its glass shade, forms. a handsome ornament to a room, while at the 
same time, it is always ready for immediate use. 
If Mr. Parkes furnishes a quality of lenses to all his microscopes 
made on this plan, similar to those attached to the instrument we had 
the opportunity of seeing at University College, we must admit he will 
prove a formidable rival to foreign instrument makers. 
There are still lower priced instruments, which are extremely well 
adapted for educational purposes, now being manufactured by Messrs. 
Highley, Pillischer, Baker, and Smith and Beck ; but the consideration 
of these we must defer to a future occasion, and for the present turn our 
attention to the binocular microscope. 
As is well known, the purpose of the binocular microscope is to 
remedy the difficulty in the way of correct observation, arising from 
our having to view an object with only one eye. Mr. Wenham, by a 
very simple contrivance, has accomplished this in a most satisfactory 
manner, at least, as far as low magnifying powers are concerned ; there 
is still, however, room for improvement with respect to high magnify- 
ing powers. By means of a small prism mounted in a brass box 
which slides into the draw tube immediately over the objective, the 
rays of light proceeding from the object are reflected in two directions, 
which by means of a double body are conveyed to both eyes, and 
thereby give a stereoscopic view of the substance under observation. 
This is a most important point gained, when uneven surfaces are being 
examined, because it enables the observer at once to judge of the posi- 
tion, form, and relative distance of the various parts without altering 
the focus of the microscope. 
So valuable, indeed, has this improvement been considered, that all 
opticians are now prepared to attach an additional draw tube and 
prism to any of the ordinary uniocular instruments, and thereby make 
them answer both purposes. For be it remembered, that the attach- 
ment of a binocular body in no way interferes with the employment of 
the instrument as a single-eyed microscope. 
As it is impossible, in this short review, to describe all the varieties 
of binocular microscopes now placed before the public, we must limit 
our remarks to the one which we consider the most perfect. 
The binocular, which we believe is most deserving of this title, is 
that just brought out by Mr. Collins (of Titchfield Street, Portland 
Place, London). It is constructed on the model suggested by Pro- 
fessor Harley, and contains all the recent improvements for combining 
rapidity of application, with simplicity in manipulation. Indeed, so 
far as the saving of time is concerned, we scarcely know how a change 
for the better could be devised. It possesses also the further advan- 
tage of having the apparatus so arranged as to render it a matter of 
difficulty to put it out of order. The whole apparatus of the instru- 
ment, prism, polariscope, stage condenser, objectives of both high 
and low powers, &c., &c., are attached to the microscope itself, and 
that, too, in such a manner as to enable the observer to place them 
in soract position without the turn of a single screw, or a moment’s 
elay. 
