BY MOLECULAR COALESCENCE. 43 
It now remains to consider to which of these forees—the 
attracting or the separating one—the production of crystals 
as shown in this experiment, is due. Before proceeding 
further, I may observe, that the evidence, both rational 
and experimental, is altogether in favour of the latter. It 
was noticed in the last experiment that rhomboidal 
crystals, formed in the crystals of triple phosphate, re- 
sembled in every respect those formed in the globules com- 
posed of triple phosphate and carbonate of lime. Hence, 
in the case of these crystals, where the only force acting 
upon their molecules is repulsive, as shown by the fact of 
their form being crystalline, the mere change in the 
arrangement of their molecules from one rectilinear figure 
to another, presents nothing indicative of attraction, but 
quite the contrary ; and therefore, in this instance, a re- 
pulsive force must be inferred to be the sole agent con- 
cerned in their production. Now, it must be particularly 
noticed, that this observation applies only to the primary 
act of giving to the molecules their first form, that is, to 
the production of the first or primative crystals; for after- 
wards these forms are joined together, and so made into 
crystals of different sizes by the action of gravity. There 
is a circumstance connected with this experiment requir- 
ing especial notice, as calculated to throw some light 
upon the nature of this and the repulsive or separating 
force. The circumstance to which I refer is the sudden 
and instantaneous manner in which perfect crystals are 
formed, differing in this respect so much from the slow 
and gradual manner in which the globules are produced. 
The latter can be seen to be produced by the coalescence 
of particles of all sizes, but of no exact geometrical figure, 
though all curvilinear, and to increase in their dimensions 
by successive coalescences or stages, one stage imper- 
