DAVIES, ON CRYSTALLIZATION AND THE MICROSCOPE. 2]1] 
of the salt, and allowed it to crystallize very slowly and un- 
disturbed. From some numbers of experiments I obtained 
Photograph No. 3. 
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four specimens of pure and decided form, the largest of 
which was about one-tenth of an inch in diameter. Some 
of these I exposed a long time to the atmosphere, but could 
not perceive any results from that exposure, as the salts were 
perfectly unchanged. 
As we are not here wishing to give the treatment required 
by each salt, but the different classes of treatment, it will 
not be lost time to bring forward a most beautiful crystal 
produced in a manner rather foreign to the last : 
Tartrate or Sopa.—Tartaric acid belongs to System V, 
the oblique prismatic, and gives very fine colours with 
polarized light. When crystallized, however, upon a slide 
the forms are not particularly striking, as there is no uni- 
formity in the design. The centre of each crystal may be 
well defined, but just m the midst of the rays an irregular 
angular mass is often placed, destroying all beauty of design ; 
and crystals without these intruders are extremely rare. It 
may be also mentioned that carbonate of soda belongs to 
the same system of crystals. To prepare—a strong solution 
of tartaric acid in distilled water should be made, and the 
