8 FORMATION OF SHELLS OF ANIMALS, ETC., 
therein are not quite so clear as those adherent to the 
lower surface of the shde, but in many respects they are 
more like natural calculi. 
The smaller ones are more accurately elliptical than 
those on the slide, the mechanical conditions under which 
they are formed being less interfered with by the attrac- 
tion of the glass. 
Among the facts deducible from a careful examination 
of the results of these experiments, the most remarkable 
and important is the perfect coalescence imto one of two 
or more globules of carbonate of lime, as much as >4;5 of 
an inch in diameter, perfectly transparent, of a hardness 
nearly equal to that of glass, and giving the sensation, 
when rubbed forcibly by the finger on a smooth, hard 
surface, of small glass beads; the imeorporation of these 
globules being so complete, that the resulting one has the 
same spherical form, the same degree of transparency, 
and the same hardness and structure as the component 
ones. Let it be observed, moreover, that this is effected 
without any possible assistance from the application of 
external force or pressure, and that therefore it can only 
be produced by the mutual attraction of the two globules. 
Now, in order thoroughly to understand the cause of 
this singular fact, and the manner in which the physical 
forces, upon whose operation it depends, act in producing 
it, every step of the process will require to be carefully 
and minutely considered. For this purpose, small por- 
tions of the two solutions before mentioned may be intro- 
duced under a piece of thin glass fixed to a microscopic 
slide, and examined by the microscope with different 
magnifying powers while the solutions are blending 
together and the carbonate of lime is in progress of for- 
mation. The appearance which is first visible is a faint 
