THE 
EDINBURGH 
PHILOSOPHICAL JOURNAL. 
Art. I . — On Crysialliscdion. By H. J. Brooke, Esq. F.B.S. 
Ijittle is at present known concerning the nature of those 
forces or influences which determine mineral bodies to assume 
a crystalline form, or concerning the causes which produce such 
a diversity of forms among crystals. Haliy states, that when 
the molecules of a body are suspended in a fluid, which after- 
wards^ either by evaporation, or through some other cause, aban- 
dons them to their reciprocal affinities, if no disturbing force 
should interfere, the molecules would unite by those planes the 
most disposed to such union, and would, by their combination^ 
produce the regular solids which we term Crystals.” 
But this explanation of the manner in which a change of state 
from solution to solidity may take place, does not assist our in- 
quiry into the nature of the causes which predispose the mole- 
cules to form solids of particular shapes, or which determine 
particular planes of those molecules constantly to unite with each 
other. 
We may, for the purpose of adapting a theory to the facts we 
observe, suppose the molecules of bodies influenced by different 
forces ; one of which acts only within very small distances, and 
may be termed the cohesive force ; the others, acting at greater 
VOL. XII. NO. ^ 3 , JAN. 1825 . 
A 
