BY MOLECULAR COALESCENCE. 55 
their molecules must be displaced from the position which 
they had occupied in relation to the centres of these two 
spheres, and be disposed around the centre of one sphere, 
containing all the molecules, which, before coalescence, 
were contained in the two. This part of the process of 
coalescence was called molecular disintegration. Now, 
there is another case in which exactly the same physical 
process takes place, but under different circumstances, 
and is therefore attended with different results. This I 
shall call final or complete molecular disintegration. It 
would seem, on examining specimens showing this pro- 
cess, to consist in the complete separation and dispersion 
of the molecules of certain compound calculi, leading to 
their total disappearance. But the fact is, that their 
molecules, in the place of becoming, after disintegration, 
collected into one large calculus, as in the disintegration 
before noticed, join together to form numerous small ones 
of different shapes, becoming dumb-bell ellipses or sphe- 
rules, some of such extreme minuteness as only to be just 
visible by the microscope. The process by which this is 
effected, and the physical conditions under which it takes 
place, will form the subject of the present article. It will 
be seen, on referring to page 40, that the spherical figure 
of the calculi, composed of a mixture of carbonate of lime 
and triple phosphate, is referred to two kinds of attrac- 
tion, namely, universal attraction or gravity, and that 
attraction which exists in a greater or less degree in all 
animal and vegetable fluids, called tenacity or viscidity, 
which, for convenience sake, I have called the attraction 
ot tenacity. The former of these forces, acting at sensible 
distances, brings the particles of these calculi into con- 
tact, that is, within the range of the attraction of tenacity, 
which, acting only at insensible distances, must have been 
