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^ has suggested a method of recording 
crystal systems in the note-book which will be found simple and 
rapid. 
Orthorhombic 
Isometric 
Monoclinic 
Tetragonal- 
Hexagonal or 
Triclinic 
Hemihedrism may be indicated by 2 written upon the symbol 
thus, 
1 Letters to the author, Dec. 6, 1918, Jan. 4, 1918. 
