226 CEMENT-CELLS. THIN-GLASS CELLS. 



of an inch in diameter, traced upon the "brass), and being held 

 by the springs with which it is furnished, a camel-hair pencil 

 dipped in the varnish to be used (Asphalte or Black Japan is 

 the best) is held in the right hand, so that its point comes into 

 contact with the glass, a little within the guiding circle just 

 named. The Turn-table being then put into rotation with the left 

 hand, a ring of varnish of a suitable breadth is made upon the 

 glass ; and if the slide be set-aside in a horizontal position, this 



Fig. 103. 



Shadbolt's Turn-table for making Cement-Cells. 



ring will be found, when dry, to have lost the little inequali- 

 ties it may have at first presented, and to possess a very level 

 surface. If a greater thickness be desired than a single appli- 

 cation will conveniently make, a second layer may be laid-on 

 after the first is dry. It is convenient to prepare a number 

 of these cells at one time, since, when 'the hand is in,' they 

 will be made more dexterously than when the operation is per- 

 formed only once ; and it will be advantageous to subject them 

 to the warmth of a slightly -heated oven, whereby the flattening 

 of their surface will be more completely assured. The Microscopist 

 will find it a matter of great convenience to have a stock of these 

 cells always by him, ready prepared for use. 



167. Thin-Glass Cells. — For the reception of objects too thick 

 for Cement-cells, but not thicker than ordinary Thin-glass, Cells 

 may be advantageously constructed by perforating pieces of Thin- 

 Glass with apertures of the desired size, and cementing these to 

 glass-slides with marine-glue. For making round cells, the per- 

 forated pieces that sometimes remain entire after the cutting of 

 disks (§ 149) may be employed, the disks often falling-out of 

 themselves when the glass is laid aside for a few days ; and thus 

 the same piece of thin-glass may afford a plate, which, when 

 cemented to a glass-slide forms a cell, and a disk suitable as the 

 cover to a cell of somewhat smaller size. There is great danger, 

 however, of the cracking of the surrounding glass in the cutting 

 out of the disk, especially when this is of large size ; and it will 

 generally be found a saving of trouble to employ the method re- 

 commended by Dr. L. Beale, which consists in attaching a piece 



