444 
POPULAR SCIENCE REVIEW. 
was so arranged that a constant circulation of warm water was kept up in a 
closed system of tubes, the temperature of which was regulated hy a mer- 
curial gas-regulator, and measured by a thermometer, the bulb of which lay 
close to the central chamber. 
How to make Atomic Lenses. — This very valuable prescription is given 
by Mr. F. Wenham, V.P., R.M.S., in the “ Monthly Microscopical Journal ” 
for July. His account is as follows : “ Strips of clear thin window-glass were 
drawn out into threads with the blow-pipe flame ; a portion was then held 
in the point of the flame and fused into a spherule of the desired size. A 
number of these may be formed in a short time. The spherical flgure is 
pretty accurate up to one-twentieth of an inch in diameter. One precau- 
tion must be observed. The strips of glass from which the threads are 
drawn must be broken, and not cut of with a diamond ; if so, the spherules 
will not retain a clear polished surface, as the rippled cut of the diamond 
leaves its mark to the last. The blow-pipe may be an ordinary portable 
one, and the flame of a common stearine candle gives heat enough. The 
glass used should be quite clean, and always be held as near the point of 
the flame as possible, in order to avoid the deposit of smoke. Large sphe- 
rules so made take an elliptical flgure. Should they be required above one- 
twentieth they are best formed thus : — Select a clean fragment of window- 
glass, broken off (not cut), of such a bulk as will form the desired sphere. 
Attach this by one corner, with heat, to the point of a platinum or iron 
wire. Now rotate the mass while in a state of semi-fusion by twirling the 
wire back and forwards between the finger and thumb, holding it sometimes 
up or down, horizontally or inclined, according to the way that the glass 
seems inclined to sink. With very little dexterity spheres up to one-fifth 
of an inch in diameter may be so obtained, the rotation of the wire enabling 
the figure to be appreciated with some accuracy. When cool the spheres 
are pulled off the wire, which enters but a little way. These spheres are 
useless things enough alone.” 
The High-power Definition of Organic Particles. — On this subject a short 
but important paper appears in the “ Monthly Microscopical .Tournal ” for 
September. Dr. Pigott, F.R.S. (the author), endeavours to show that the 
markings on a Podura are purely spherical, just like those on Angulatum. 
Progress of Microscopy in England during the last Three Months. — The 
following is a list of the titles of the several papers which have appeared 
in the “ Monthly Microscopical Journal ” for July, August, and September : — 
Observations on the Optical Appearances presented by the Inner and 
Outer Layers of Coscinodiscus when examined in Bisulphide of Carbon 
and in Air. By J. W. Stephenson, F.H.A.S., Treasurer R.M.S., and 
Actuary to the Equitable Assurance Society. — Remarks on Aulacodiscus 
formosus, Omphalopelta versicolor, &c., with Description of a New 
Species of Navicula. By F. Kitton, Norwich. — Measurement of Im- 
mersed Apertures. By F. H. Wenham, Vice-President R.M.S. — On 
Bog Mosses. By R. Braithwaite, M.D., F.L.S. — On the High-Power 
Definition of Minute Organic Particles. By Dr. Royston-Pigott, M.A., 
F.R.S. , F.C.P.S., F.R.A.S., M.R.I. — The Preparation of the Brain and 
Spinal Cord for Microscopical Examination. By H. S. Atkinson. — 
Researches on the Life History of a Cercomonad : a Lesson in Bio- 
