ZOOLOaY AND BOTANY, MICEOSCOPY, ETC. 703 



edge is just larger ttan the cell to be used. The cell is then laid 

 on, centered, and pressed hard to set it. If the slide is slightly 

 ■warm and the cement thick, it will not run at all, but will hold the 

 cell firmly in place, so that the cover can be put on at once. If 

 it is thin, it must first be allowed to harden somewhat. "When ready, 

 as it will be in a few moments if properly managed, a ring of the 

 same cement is run on the cell, and the cover is then laid on, pressed 

 down, clipped in position, and the mount laid aside to harden. It is 

 well in an horn' or so to remove the clip and run cement in the joints 

 between cover-glass cell and slide, in order to be certain that no air- 

 holes remain. It can then be reclipped, and set aside until the 

 cement is perfectly hard. The mount is complete, and -nill last a 

 long time if proper care is taken of it. For security it is well 

 to put on additional rings of cement more elastic than the shellac, 

 and to make a final finish for the sake of appearance. A ring of 

 white zinc cement should therefore be put on, which completely fills 

 up the joints, and makes a smooth surface from cover-glass to slide. 

 This must harden several days, and the slide is then complete, unless 

 additional rings are run on for a finish. 



In making the rings on slides it is not always easy to make the 

 edges true, and sometimes the cement spreads too far. In such cases 

 they should be turned down with the point of a knife until they suit. 

 If the cement is taken just at the right time this is easily done, and 

 it improves the appearance very much. 



Mr. A. Y. Moore also commends * tin-foil cells, which he makes 

 as follows : — 



Flood a clean icarm slide with lacquer (a weak solution of shellac 

 and alcohol), allowing it to drain from one corner. The heat of the 

 slide causes a rapid evaporation of the alcohol, leaving a film of shellac 

 on the slide. Prepare a piece of clean flat tin-foil, a little larger than 

 the outer diameter of the cell required. Heat the slide till the film of 

 shellac is melted, taking care not to boil it. The foil should then be 

 placed upon the centre of the slide, and firmly pressed against it, so 

 that it may adhere at all points. In a few minutes the slide will be 

 cool, and the film firmly adherent. It may now be placed upon the 

 turntable, and with the point of a sharp knife-blade two clean cuts 

 should be turned through the foil, one for the outer and one for the 

 inner edge of the cell. As soon as the cuts are made, the superfluous 

 tin should be scraped away and the slide cleaned with alcohol ; it is 

 then ready for use. The cement is hard, and no time need be wasted 

 in waiting for it to dry, as in. ordinary cells. 



"Wax Cells. t — Mr. W. H. Gilburt finds, as the result of using wax 

 for a long time past, that dewing is avoided by building up the cells. 

 He spins up the wax on the slide, using melting wax and a turntable. 

 The cover adheres by itself, and he has not found any condensation 

 of moistm-e whatever, the heating of the wax seeming to get rid of the 

 volatile element. In finishing ofl', it is best to use first a thin coating 



* Amer. Journ. Micr., vi. (18S1) pp. 29-30. 



t Joui-n. Quek. Micr. Club, vi. (18S1) pp. 215-6. 



3 A 2 



