VIII. On the Form of the Integrant Molecule of Carbonate of Lime. 
By DAVID BREWSTER, ll.d. f.b.s. lond. & ed. 
MEMBER OF THE GEOLOGICAL SOCIETY. 
[Read 3d April, 1818.} 
F ROM the facility with which carbonate of lime yields to me- 
chanical division, its primitive form was determined by Mr. Keir, of 
Birmingham, and by Assessor Gahn, in Sweden, long before crystal- 
lography, in the hands of the Abbe Haiiy, had assumed the form and 
dignity of a science. When this eminent mineralogist found that it 
refused to be divided in any other direction than by cleavages 
parallel to the sides of its rhomboidal nucleus, he concluded that the 
form of its integrant molecule was an obtuse rhomboid. This con- 
clusion was implicitly adopted by mineralogists, till the Count de 
Bournon announced the discovery of cleavages passing through the 
long diagonal of its rhomboidal faces, and maintained that the form 
of its integrant molecule was a triedral prism with inclined bases, or, 
one half of the primitive rhomboid divided by a section passing 
through the long diagonals of two of its opposite planes. Count 
Bournon acknowledges that in many specimens this cleavage was 
extremely difficult to be obtained ; that in others it was impossible 
to overcome the cohesion of the molecules in the direction of the 
l 2 
