MOUNTING IN CELLS 



447 



B 



ous sizes be made by this simple method, but, by flattening the tube 

 (when hot) from which they are cut, the sections may be made qua- 

 drangular, or square, or oblong (C, D). For intermediate thicknesses 

 between cement-cells and glass ring-cells, the Editor has found no 

 kind more convenient than the rings stamped out of tin, of various 

 thicknesses. These, after being cemented to the slides, should have 

 their surfaces made perfectly flat by rubbing on a piece of fine grit 

 or a corundum-file, and then smoothed on a. Water-of-Ayr stone ; 

 to such surfaces the glass covers will be found to adhere with great 

 tenacity. The ebonite and bone cells are cheap, and also easy of 

 manipulation. They are specially useful for dry mounts. 



The glass slides and cells which are to be attached to each other 

 must first be heated on the mounting plate ; and some small cuttings 

 of marine glue are then to 

 be placed either upon that 

 surface of the cell which is 

 to be attached, or upon 

 that portion of the slide 

 on which it is to lie, the 

 former being perhaps pre- 

 ferable. When they begin 

 to melt, they may be 

 worked over the surface of 

 attachment by means of a 

 needle point ; and in this 

 manner the melted glue 

 may be uniformly spread, 

 care being taken to pick 

 out any of the small gritty 

 particles which this cement 

 sometimes contains. When 

 the surface of attachment 

 is thus completely covered 

 with liquefied glue, the cell 

 is to be taken up with a 

 pair of forceps, turned 

 over, and deposited in its 

 proper place on the slide; and it is then to be firmly pressed dou n 

 with a stick (such as the handle of the needle), or with a piece of 

 flat wood, so as to squeeze out any superfluous glue from beneath. 

 If -any air-bubbles should be seen between the cell and the slide, 

 these should if possible be got rid of by pressure, or by slightly 

 moving the cell from side to side ; but if their presence results, as is 

 sometimes the case, from deficiency of cement at that point, the cell 

 must be lifted off again, and more glue applied at the required 

 spot. Sometimes, in spite of care, the glue becomes hardened and 

 blackened .by overheating ; and as it will not then stick well to 

 the glass, it is preferable not to attempt to proceed, but to lift off 

 the cell from the slide, to let it cool, scrape off the overheated glue, 

 and then repeat the process. When the cementing has been satis- 

 factorily accomplished, the slides should be allowed to cool gradually 



D 



FIG. 315. Glass ring-cells. 



