Nolices respecting New Books. 69 
ote. Atheory has lately been advanced * by M. Prechtl, 
which attempts to account for various crystalline forms 
from the different degrees of compression that soft spheres 
may be supposed to undergo i in assuming the solid state. 
‘Tt is supposed, that with a certain degree OF softness and of 
relative attraction, the particles will be surrounded each by 
four others, and will all be tetrahedral, although in fact ut 
be demonstrably impossible that tetrakedrons alone should 
Gill any space. 
It is next supposed, that.soft spheres less compressed will 
be surrounded by five others, and will be formed into trian- 
gular prisms, comprised amder five similar and equal planes. 
That they should be similar is impossible ; and it is further 
demonstrable, that when the triangular termination of such 
a prism is equal in area to each rectangular side of the 
prism, so as to present equal resistance, “according to the 
hypothesis, then the triangular faces will be nearer to the 
centre in the proportion of three to four, so that the attrac- 
tions will not be equal, as the hypothesis would require. 
A third hypothesis of M. Prechtl is, that the degree of 
co mpressibility may be such that each particle will be sur- 
rounded by six others, giving it the form of a cube, which, 
it must be admitted, 1s.a yery possible supposition. 
All further application of the same hypothesis is pre- 
cluded by M. Prechtl, by denying that one particle can be 
surrounded by more than six others; although in fact it is 
most evident, that ayy sphere when not compressed will be 
surrounded by twice that number, and conse quently bya 
slight degree of compression will be converted into a dode- 
cahedron, according to the most probable hypothesis of 
stmple compression. 
XIIL. Notices respecting New Leoks. 
Parr I. of the Philosophical Transactions for 1813 has 
eh its appearance. ‘The following are rts contents: 
On a new detonating Compound, i in a Letter from Sir 
Humphry Davy, LL.D.¥. Me S. to the Right Hon. Sir Joseph 
Banks, Bart. K.B. P.R'S.—2. On a remarkable Application 
“of Cotes’s Theorem. By i. FW. Herschel, Esq. Com- 
municated by W.. Herschel, LL.D. F. R.S.—3. Observa- 
tion of the Summer Solstice, 1812, at the Royal Observa- 
tery. By John Pond, Esq. Astronomer Royal, PRS. 
4. Observations relative to the near and distant Sight of 
* Journal des Mines, No. 166, 
E3 different 
