The Microscope. 45 



with ether before the alcohol is used. The broken gum should 

 be soaked in the ether in a closely-stoppered bottle, until suffi- 

 ciently swelled, when the excess is poured off, the alcohol added 

 and the solution treated as already described. 



Although this cement dries rapidl}'^ and will cling tenaciously 

 to the glass, it may be forced to adhere more closely and to dry 

 more quickly, by holding the freshl}^ made cell over the lamp 

 flame. This should be done until the cement will be hard as 

 bone when cold, but so carefully that it shall not boil. In that 

 case the ring will be spoiled, as the bubbles will be permanently 

 entangled, and the surface made uneven and irregular by them. 

 When cold, the ring will be so closely adherent to the glass that 

 a knife and some labor will be neccssar}^ to remove it. Cells 

 made in this way are admirable for preparations of an}* kind, 

 even for balsam mounts, that may then be finished with a ring 

 of balsam dissolved in chloroform. The reader of course under- 

 stands that onl}' the empty cell should be heated, not the mount 

 after the shellac has been applied to the cover glass. 



king's cements. 



These are a series of cements made by the Rev. J. D. King, 

 of Cottage City, Mass. Their composition is a secret. Those 

 that have used them recommend them, with much praise for their 

 good qualities. They are beautiful when applied to the mount, 

 as they are perfectly transparent and delicately colored. If the 

 reader should prefer to buy these he will not be disappointed in 

 the result, and they are not expensive. Shellac is probably 

 their chief constituent. 



WHITE ZINC CEMENT. 



Let me introduce what I have to say about white zinc cement 

 by the statement that personally* I have never used it. All my 

 experience with it has been my experience with it as used by 

 others, and I early became prejudiced against it. With it my 

 microscopical life has been a sad one. The material is much in 

 vogue for making- cells and for finishing; mounts, but I want to 

 warn the reader against it. I have found it the most dangerous 

 and the most treacherous thing that the microcopist can employ. 

 My experience and m}'- observation of its action are, as I have 

 said, confined to slides received in exchange or bought from one 



