OF THE MICROSCOPE. 223 



BLACK JAPAN. "When this can be procured of good quality, 

 it makes a very excellent cell. It adheres very firmly to the 

 glass provided the latter be exposed to a moderate heat after 

 the cement has become dry. Black Japan dries up and thick- 

 ens when kept, but may be thinned with turpentine. 



BRUNSWICK BLACK. This is simply a solution of asphaltum 

 in turpentine. Occasionally it is rendered very black by the 

 addition of a little lampblack. When good, it makes a very 

 excellent cement. Its quality depends chiefly upon the char- 

 acter of the asphaltum that is used in its preparation. Now 

 there are several varieties of asphaltum in market, the most 

 common kind at the present day being that obtained from coal 

 tar. This seems to be entirely unfit for the purpose. The 

 proper kind is that which is found native in several parts of the 

 world. The two kinds are easily distinguished by their odors. 



SHELLAC. This well known substance, when dissolved in 

 alcohol, forms a varnish or cement of great value to the micro- 

 scopist, and is the proper one to be used when glycerine is em- 

 ployed. Much of the shellac in market is artificially made 

 from resin and wax, and makes a poor varnish. Keal shellac 

 must be employed if failure would be avoided. 



BELL'S CEMENT. -^Carpenter states that this cement is merely 

 shellac dissolved in alcohol. With us it has presented no ad- 

 vantage over other cements. 



SEALING WAX VARNISH. This is prepared by dissolving the 

 best sealing wax in alcohol. It unfortunately happens that all 

 the fancy colored sealing wax in market is of inferior quality. 

 Very excellent red wax may be obtained, but we have never 

 been able to obtain good blue, black, green or other colored 

 wax. We therefore make varnish of these colors by dissolv- 

 ing in alcohol the materials used for making the best red wax, 

 substituting some other color, however, for the vermillion. 



COLORED SHELLAC. Bleached shellac, dissolved in alcohol, 

 and colored with aniline blue, red, etc., makes a very fine trans- 

 parent varnish. 



