68 THE NORTHERN MICROSCOPIST. 
developments of science; R. Fletcher, F.C,S., on self-acting do- 
mestic help; C. W. Maybury, F.C.S., on chemical philosophy ; 
and W. Rideout, on the life history of Dytiscus marginalis. Dr. 
Evans is set down for a paper, and two evenings are devoted to 
short communications. ‘The library is now available to the mem- 
bers, offices having been taken in a central situation in the city, 
where books are delivered to the members daily. 
SLIP-CLEANING INSTRUMENT.—Mr. Searle brought this instru- 
ment before the notice of the members of the Postal Microscopical 
Society at their last meeting. It consists of a flat piece of wood 
154% % inch. Along each side of this and close to the edge is 
fastened a slip of wood 12x %4 x ¥% inch, thus leaving a clear 
space of 3 inches between them, and in which the slips are ar- 
ranged for cleaning. Two other loose strips 14 x % x ¥ inch are 
now placed upon the ends of the glass and are each secured at 
one end by being slipped into a staple. That portion of the wood 
on which the slip rests is padded with cloth. The rubber for 
polishing the centre of the slips is made by glueing two thicknesses 
of cloth on the end of a large cotton reel, a piece of wash-leather 
is stretched over the cloth and secured by being tied to the 
middle of the reel. Mr. Searle says it is desirable to have two of 
these padded reels, one to use with putty powder, the other to give 
the final polish. 
THe Tuses oF Inrusor1A.—Engel thinks that the tubes of In- 
-fusoria have a composition analogous to cellulose, seeing that they 
behave in a similar manner with both mordants and dyes. 
WuiTeE Zinc VARNISH.—This semi-fluid substance is made in a 
variety of ways; but one which I always adopt, and which yields 
me very good results is as follows:—The pigment is very finely 
divided oxide of zinc and the vehicle necessary to hold it in suspen- 
sion Is gum dammar dissolved in benzol. Take equal parts by weight 
of gum dammar and the finest oxide of zinc, dissolve the former 
in twice its weight of benzol, and when dissolved pour it into a 
mortar where it is to be mixed up with the oxide of zinc. The 
pestle must be used vigorously, and if required thinner it may be 
let down with benzol, or if thicker some of the solvent may be 
allowed to evaporate by exposure for a short time in a saucer or 
flat dish,—/ack /. 
CaTcHING Popur#.—These insects are to be found in damp 
warm cellars, or warm cupboards of old houses, under flower-pots 
and stones, in vineries and hothouses, and in many other similar 
places. They are mostly of a dull leaden color, wingless, and do 
