124 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
He had very carefully examined this instrument, and had made 
measurements of all its parts and calculated its focal distances, and 
thought it would he interesting to give these particulars. Like many 
of these older Microscopes, it was fixed to the box, but to the inside 
and not upon the outside as was usually the case. It could not be 
taken out of the box, as it was fixed to the inside with a compass 
joint. Size of box, 12*8 in. long by 5-5 in. wide, by 5 in. deep. 
The total length of the body from eye-cap to nose-piece is 7J in., 
and from nose-piece to field-lens 5*3 in. 
The stage measures 2J by 3J in., and is fitted with rackwork by 
means of which it is adjusted to focus, and there are spring clips pro- 
vided for holding the slide. 
The concave mirror is 2 in. in diameter, with a focus of 3^ in- ; no 
plane mirror is provided. 
The pillar is in length 9 J in., and in section \ in. square ; the 
limb is fixed, the centre projecting 1*8 in. beyond the pillar. 
The eye-piece has a doublet compound eye-lens formed of (1) a 
bi-con vex lens with ratio of radii (probably) 1:2, the flatter side being 
toward the eye, diameter 0 • 8 in., focus 1*3; (2) placed close to the first, 
an equiconvex lens, diameter 0 * 9 in., focus 1 * 5 in. ; (3) a field-lens placed 
at a distance of 1 • 5 in. from the inner eye-lens ; this is also equiconvex, 
diameter 1*5 in., focus 2 # 7 in. The joint focus of the two eye-lenses 
being 0*9 in., and of the whole eye-piece 1*25 in., giving it a magnifying 
power of x 8. 
The objectives he found to be as follows : — 
No. 1, equal to about a 1 in., power X 50 — achromatism bad — shows 
coarse areolations of Triceratium favus, and ribs in main cut suctorial 
pipe in blow-fly’s tongue. 
No. 2, equal to about a 1/2 in., power X 85 — achromatism good — 
will not show T. favus. 
No. 3, about a 1/3, power X 120, resolves coarse structure of Eupo- 
discus Argus and ribs in main cut suctorial pipe of blow-fly’s tongue ; 
achromatism not so good as that of No. 2. 
No. 4, about a 1/7, is the garnet lens, power x 280, resolves primary 
structures in T. favus , definition very bad. 
No. 5, about a 1/9, power x 360, lens equiconvex, achromatism 
fairly good, resolves all the bars and small hairs in blow-fly’s tongue, 
and primary structure of Coscinodiscus. 
No. 6, about a 1/10, the best of the series, a doublet, piano over equi- 
convex, power X 400, achromatism fairly good, resolves Cymbella gas - 
troides, Actinocyclus Balfsii, and all details of blow-fly’s tongue. 
The low power has a large opening, and is consequently very fluffy, 
but there is a minute hole only at the back of the higher powers, by 
which the aperture is cut down and rendered exceedingly small. The 
resolving power is therefore, in the case of the very best lens of the 
series, only about equal to a 1^ in. objective at the present day. 
Two Old Microscopes. — At the meeting of the Society held on 
December 15, 1897, the President drew attention to two old Microscopes 
exhibited by Mr. C. L. Curties. The first of these was a Hartnack 
model, non-inclinable, push-tube coarse, and direct acting screw fine 
adjustments, plain stage with small round hole, concave mirror, and 
