1900] MICROSCOPICAL JOURNAL. 233 



the purpose. With a little practice, however, it is quite 

 easy to hold half the cover-glass in a piece of chamois 

 leather between the finger and thumb, but not edgeways, 

 and to polish, the other half, turning the glass round 

 meanwhile. 



Dry Mounting. — The mounting of opaque objects and 

 of objects that can be mounted dry, is comparatively sim- 

 ple. The various apparatus, reagents, media, stains, etc. , 

 will be mentioned as we proceed, and their uses will then 

 become apparent at the same time. Accordingly we shall 

 here require a turntable. This is a circular brass plate 

 about 3J inches in diameter, mounted so as to rotate upon 

 a centre, the upper surface of this plate having concen- 

 trict rings engraved upon its surface. .These latter serve 

 as a guide in centering the slide upon the rotating plate. 

 There is also a pair of clips to hold the slide in place. The 

 turntable is mounted on a wooden block or iron stand 

 which serves as a support for the hand. The cost will be 

 about six shillings. We do not recommend the "self-cen- 

 tering" turntables. We shall also need two or more good 

 sable brushes, which are best and cheapest in the long run. 

 These should be about 1-16 inch and 3-32 inch in diameter, 

 costing ninepence or one shilling each. Also a pair of 

 steel or brass forceps, not too narrow, costing one shill- 

 ing and sixpence, a bottle of gold-size, a bottle of Bruns- 

 wick Black, and a bottle of gum arabic. All of these are 

 obtainable from the opticians. 



The usual plan with opaque objects is to place a slide 

 on the turntable, centre by means of the concentric rings, 

 and then run a disk of Brunswick Black of the requisite 

 size in the centre, rotating the stage meanwhile by means 

 of the forefinger of the left hand and the milled head 

 beneath. As soon as this black disk is dry, a piece of 

 black paper of the same size is cut out and gummed upon 

 it. The black paper should not have a glazed surface. 

 Then upon the disk is built up a cell of the requisite depth 



