Dr. Eafon on Cryftallization. S r 
In the firft of thefe cafes, the cryftallization 
is carried on by the feparation of the fluid which 
keeps the cryftallizable body in a ftate of locu¬ 
tion; and in- the fecond, the fame effeCt is pro¬ 
duced by the cooling of the materials, or jhe 
extraction of their heat. If, for inftance, a fo- 
lution of the foftil fixed alkali in water be-firft 
evaporated to a pellicle, and afterwards oe 
luffered to cool gradually, without being dis¬ 
turbed, the fait will fhoot into beautifully trans¬ 
parent cryftals; and in like manner, if water 
be deprived, of that degree of heat which is 
requifite to preferve it in a fluid ftate, it will lhoot 
into radii or needle-iike cryftals, which, at their 
union, form conftant angles of 6o degrees. If, 
however, the water in the firft cafe,' and the heat 
in the fecond, be feparatea with too much 
rapidity, the cryftals will be fmall, and more or 
lefs irregular, according to the celerity with 
which the procefs may have been conduced; 
The fame obfervations are equally applicable to 
all bodies of the cryftallizable kind. 
Although, in general, every cryftallizable fub- 
ftance difeovers a manifeft tendency to fhoot 
into mafles or cryftals of a peculiar form, yet we 
muft hereobferve, that the forms of thofe cryftals 
are liable to great variation from various cir- 
cumftances attending their formation. 
Gypfum, for example, is well known to be 
a vitriolic fait with a calcareous bafls, and yet 
the 
