BY MOLECULAR COALESCENCE. 61 
taken advantage of to crystallize salts, otherwise difficult 
of crystallization. The calculi formed according to this 
process are very large, being ;5th or jth of an inch in 
diameter, and spherical, excepting when they adhere to the 
side of the bottle, in which case they are flattened on the 
side attached. They are very regularly and beautifully 
laminated, and coalesce in the same manner as those above 
described. When treated with weak acetic or muriatic 
acid they effervesce, and leave a residue of amorphous 
matter. When dried they retain their globular figure, 
but show a tendency to split into segments ; their surface 
is white, and generally smooth, but they do not present 
that glassy or pearly appearance which is remarkable in 
those prepared by the other process. Under polarized 
light they present a distinct cross, and appear somewhat 
coloured; but do not exhibit the prismatic colours distinctly, 
like the other calcul. The most remarkable property of 
these calculi is the facility with which they undergo either 
partial or complete disintegration. So that they cannot 
be put up as transparent objects permanently, in any watery 
fluid. In glycerine they disappear after a few weeks, 
leaving sometimes a residue having the form of a thin 
membranous capsule. If heated a little, and then put into 
hot oil, they first become covered with a feathery coating 
and afterwards fall into large fragments. This coating 
seems to me to be produced by their separating the oleine 
from the stearine, absorbing the one and leaving the other 
on the surface. But their most smgular property is the 
partial disintegration which they undergo when removed 
from the bottle in which they were formed, and put up in 
a cell filled with the solution taken from the same bottle, 
and so secured from the access of air that no alteration in 
its density or chemical composition can take place. 
