428 Scientific Intellugence. 
The theory which I have formed to account for these facts is as 
follows. We may conceive that the molecule of mica is an elli 
soid, whose elliptical section, 
Ip- 
the normal result of their as- ~ 
sociation, as represented in fig. 
may become associated by al- 
ternate single poles to form a nucleus, such as represented in fig. 
. Such a group once formed would be in a condition of great 
stability, resulting from the concurrent action of the several poies ; 
would be a macle of a form the mineral 
kingdom. If six molecules unite in a similar way to form a nue 
stated above can only be affirmed with certainty of plates consisting of lamine 
which very nearly fulfill the conditions we have described. Very small inequalities 
of thickness renders the effect irregular, and made it at first difficult to disco 
the law. r experiments have been a series of approximations; and, althoug: 
i mpete wi 
and if now each of the molecules develops into a crystal, the result 
which is very common i 
: pproac! od ese 
result as to be able to point out with confidence one way, at least, by which the 
effects seen in natural crystals may be produced. We have usually cut the lam- 
ani 
th: 
ir thickness. It still remains to make careful quantitative measure 
3 effects produced under determinate conditions; and, as can easily be 
seen, the subject opens a wide field for mathematical analysis as well as physical 
