270 



ELEMENTARY CHEMICAL MICROSCOPY 



will be at once followed by the appearance of innumerable well 

 formed characteristic crystals. If the formation of a crystalline 

 crust cannot readily be induced, the seeding of the drop may be 

 done by taking a tiny fragment of the compound from the reagent 

 bottle, crushing it to powder upon a slide and introducing an 

 infinitesimal fragment into the drop which refuses to crystallize. 

 Note-book records should include diagrammatic sketches of 

 the crystal form, extinction, extinction angles, plane angles 



FIG. 145. Note Book Sketches of Crystals. 



whenever important, etc. Fig. 145 illustrates the way in which 

 these records may be kept. 



Dr. W. W. Andrews 1 has suggested a method of recording 

 crystal systems in the note-book which will be found simple and 

 rapid. 



Isometric U 

 Tetragonal 

 Hexagonal or 



Orthorhombic 

 Monoclinic J\ 



Triclinic 



Hemihedrism may be indicated by 2 written upon the symbol 

 thus, -jr- ^= 



1 Letters to the author, Dec. 6, 1918, Jan. 4, 1918. 



