The Microscope. 151 



GuiACUM VARNISH : gum guiacum, 2 ounces ; sheila , 2 ounces ; 

 alcohol, 10 ounces, The powdered gum guiacum is lissolved in 

 the alcohol and the powdered shellac added ; keep tlie bottle in 

 hot water until all is dissolved. 



Shellac varnish : 1, shellac, 60 grms. ; 2, alcohol, 60 grms. ; 

 3, castor oil, 25 grms. ; 4, alcoholic solution of anilin dye, a few 

 drops. 1 and 2 are dissolved and heated until quite thick, 

 then a little of 4 is added, and for every 60 grms. of the mixture 

 add 25 grms. of castor oil, and heat for a short time. 



Electrical cement : 5 parts of rosin ; 2 parts of hard balsam ; 

 1 part of yellow beeswax ; 1 part of red ochre. The components 

 are melted together. This is not usually employed for mount- 

 ing purposes, but may be used in cementing glass and metal 

 parts of instruments. 



Zinc white cement, German formula : 1, mastic ; 2, dammar ; 

 3, sandarac; 4, Venetian turpentine; 5, turpentine; 6, benzol; 

 7, zinc white. 1, 2 and 3, powdered, are mixed in a well- 

 corked bottle with 4, 5 and 6 ; shake well occasionally ; after 

 several days filter, and triturate in a mortar with zinc white in 

 quantity sufficient. Dilute if necessary with benzol. 



Zinc w^hite, English formula: 1, gum dammar; 2, gum 

 mastic; 3, benzol. Dissolve powdered 1, 2 and 3 in a well- 

 corked bottle ; when dissolved filter, and mix carefully in a 

 mortar with zinc white. 



Marine glue : India rubber shreds, 2 ounces ; shellac, 2 oun- 

 ces. Dissolve the rubber in mineral naphtha, add the powdered 

 shellac, heat until liquefied, and mix well together. This gives 

 solid marine glue, and requires heat in its application. Great 

 care should be observed in having all fire and flame removed 

 while there still remains naphtha in the mixture. 



Lovett's cement : powdered white lead, 2 parts ; powdered 

 red lead, 2 parts ; powdered litharge, 3 parts ; gold size. The 

 white and red lead and the litharge must be very finely pow- 

 dered ; for use this powder is mixed with gold size to the con- 

 sistency of cream, and the cells immediately fastened to the 

 slide. They are secure in two weeks. This stands considerable 

 heat and is excellent for fluids containing some alcohol. Make 

 a little only of the mixture with gold size at a time, as it hard- 

 ens quite rapidly and becomes useless. 



King's cement and lacqures. Satisfactory and highly recom- 

 mended by some. 



