ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
21 a 
the credit of the invention of this improvement in the Microscope stand, 
which is to-day of such great service. The improvements effected by 
him in achromatic objectives for the Microscope are already acknow- 
ledged. 
“ In the same casting as the Lister limb there is a V-shaped bracket 
7/8 in. thick ; to the upper side of this bracket the stage is screwed, and 
to its lower side a plate parallel to the stage. This lower plate carries 
a sprung tube, which forms the substage. In this substage I have a 
push-tube focussing adapter, which carries a Zeiss ‘ improved aplanatic 
lens x 10 ’ ; this lens makes a very suitable achromatic condenser for 
the powers used on this Microscope. As the lens merely slides into a 
sprung tube, it can be easily removed for its ordinary use as a * loup.’ 
Below the adapter is a Gifford’s screen. 
“ This condenser requires no diaphragm, because the objectives on the 
rotating nose-piece are a Zeiss a a, and a Reichert 8 mm. ; with the first 
the condenser gives a full cone, which the a a stands perfectly well, and 
with the second a 3/4 cone, at which point the 8 mm. performs at its 
best. The magnifying powers are 70 and 170 diameters respectively, 
the diameter of the field being 8£ in. 
“ A Microscope of this description will be found very useful, not only 
for rough work, such as the examination of unmounted objects, and for 
roughly searching finished slides, but also for a hack Microscope, as a 
companion to a larger instrument on which critical work is being per- 
formed. I am told by biologists who have done a large amount of 
Microscope work, that the employment of a second Microscope is pre- 
ferable to the use of a rotating nose-piece on the larger instrument. 
This I can well understand, because when the condenser has once been 
adjusted for critical illumination with a high power, it is very annoying 
to have to disturb it for lower-power work. 
“ Dimensions of PoivelVs Iron Microscope. 
Body, 8 in. (203 mm.) ; diameter, 1| in. (28 mm.). 
Spread of foot, 7J X 6 in. (190 mm. x 152 mm.). 
Distance of optic axis from table when the Microscope is placed in 
a horizontal position, 5J in. (140 mm.). 
Stage, 4| x 3f in. (Ill mm. x 92 mm.). 
Height of stage from table, Microscope being in a vertical position, 
4f in. (120 mm.). 
Rack extension, 2J in. (57 mm.). 
Cut in stage, wide, 1^ in. (33 mm.) ; depth, 2J in. (63 mm.). 
Distance from eye-cap to front lens, 11 in. (280 mm.). 
Weight, lb. (3 kg.). 
The brasswork is finished bright, and the ironwork japanned green ; 
cork is plugged in the feet.” 
Martin Microscope. — Fig. 46 illustrates a Microscope alleged to 
have been made by Benjamin Martin, and presented to the Society last 
year by Mr. Alfred George Fryett, of Melbourne, Australia. This has 
evidently been evolved from B. Martin’s first Microscone, which he called 
