60 THE MICROSCOPIST. 



hole in a square piece of thin glass, such as is used for covers, 

 and cementing it to the slide, will be found of use in mounting 

 delicate structures. For the thicker class of objects the tube 

 cells, or those built up with strips of glass, are most suitable. 



CEMENTS. 



Japanners' Gold-size, or Severe Dryer, is a mixture of boiled 

 linseed oil, dry red lead, litharge, copperas, gum animi, and 

 turpentine. The first and last ingredients are its principal 

 constituents. Mr. Williams, Artists' Furnishing Store, Sixth 

 Street above Market, Philadelphia, has it for sale. 



Sealing-wax Varnish consists of small pieces of sealing-wax 

 dissolved in alcohol. 



A.sphaltumy dissolved in turpentine, has this advantage, 

 that spirit may be employed as the preserving fluid if desired. 



Marine Glue is a mixture of shell-lac, caoutchouc, and naph- 

 tha. It is melted by heat. Caustic potash will remove its 

 traces from glass. Tulk and Henfrey give the following recipe 

 for its preparation : Dissolve 1 pound of caoutchouc in 4 gal- 

 lons of coal naphtha; 1 pint of this solution is mixed with 2 

 pounds of shell-lac; it is a most useful preparation for building 

 up glass cells, &c. Powdered gum arabic, made into a mucilage 

 with distilled vinegar, is said to be a very powerful cement. If 

 greater consistence is required a little calomel may be added. 



Gum Mastich and Caoutchouc, dissolved in chloroform, is an 

 excellent cement, and has the advantage of remaining fluid at 

 ordinary temperatures, while the rapid evaporation of the 

 chloroform enables the slide to be quickly prepared. This was 

 suggested by Dr. Goddard. The caoutchouc should first be 

 dissolved in the chloroform, by the application of gentle heat, 

 to the consistence of thick mucilage, gum mastich should then 

 be added until it becomes sufficiently liquefied. 



