30 
The Presidenfs Address, 
Siicli is a description of the instrument intended for the 
Society;, which^ by the kindness of Mr. Ross_, I have had an 
opportunity of inspecting and examining. 
Mr. Eoss has also constructed a new achromatic con- 
denser, giving a large field with great intensity, intended for 
use with both high and low powers : it adapts to the diaphragm 
plate of the microscope, for the modification of the illumi- 
nating pencil, and, in combination with the polarizing prism, 
will be found a great advantage^ as in polarization one half of 
the light is thrown away. 
The " Kelner^s Orthoscopic Eyepieces," though not new_, 
have this year met with a very greatly increased demand, due 
to the recognition of the advantage which their very extended 
field gives for purposes of exhibition. 
An improved compressor consists of a base plate, across 
which is fitted a dovetailed slide, carrying the lower glass. 
At one end of the base plate is another short, vertical, dove- 
tailed slide, moved by a milled head and screw ; and again on 
to this, parallel to the base plate, a frame, which holds the 
upper glass. Both glasses can be removed for cleaning with 
great facility ; the pressure applied is completely under control, 
and as the glasses remain parallel whatever the separation, 
the object under manipulation is not slid about by unequal 
pressure. 
Messrs. Smith, Beck, and Beck remark, The most notice- 
able feature of the past year has been, that microscopists are 
returning to the use of object-glasses of moderate aperture, 
but with the corrections made as perfect as possible.^'' This 
they think " may be attributable to the introduction of the 
binocular principle, which opens up a new field of observa- 
tion amongst general objects which mostly require illumina- 
tion from above.-" Very few of the better class of instru- 
ments, I am told, are now made with a single body, and 
great numbers have been returned to the makers, to have 
binocular adaptation. 
From memoranda kindly furnished by the three firms 
above-mentioned, I am able to state that the demand for 
microscopes has continued to increase, " in spite of the bad 
state of trade generally, and the entire stoppage of any 
supply to America." The number of microscopes sold by 
these three houses during the year is considerably above 
600 ; " the sale of instruments of the very highest class 
maintains its full proportion of increase ;" the number ex- 
ceeds 100. One of these houses alone has supplied to the 
public during the last year 360 object-glasses of the very 
highest character. 
, The demand for mounted objects for the microscope is, I 
