76 THE MICROSCOPIST. 



so as to thicken it, the whole boiled again, and the fluid 

 poured off for use. 



Bell's Cement is said to be best for gtycerin specimens. 

 It appears to be shellac dissolved in strong alcohol. 



Brunswick Black is asphaltura dissolved in turpentine. 

 A little india-rubber dissolved in mineral naphtha is some- 

 times added. 



Canada Balsam in chloroform or Dammar varnish (page 

 74) is often used as a cement. 



Marine Glue. This is most useful in building glass 

 cells, etc. It consists of equal parts of shellac and india- 

 rubber dissolved in mineral naphtha by means of heat. 



Electrical Cement is made by melting together 5 parts 

 of 'rosin, 1 of beeswax, and 1 of red ochre. 2 parts of 

 Canada balsam added make it more adhesive to glass. 



White, hard Varnish, or gum sandarac, dissolved in 

 alcohol and mixed with turpentine varnish, is sometimes 

 colored by lampblack, sealing-wax, etc. 



White Zinc Cement. Oxide of zinc rubbed up with 

 equal parts of oil of turpentine and 8 parts of solution of 

 gum Dammar in turpentine of a syrupy consistence, or 

 Canada balsam, chloroform, and oxide of zinc. 



CHAPTER VI. 



MOUNTING AND PRESERVING OBJECTS FOR THE MICROSCOPE. 



FOR the permanent preservation of specimens, various 

 means are employed, according to the nature of the object 

 and the particular line of investigation desired. Few, if 

 any, objects show all their peculiarities of structure or 

 adaptation to function, and for scientific work it is often 



