On the Clinochlore of Chester Co., Pa. 223 
after removal of the baryta by sulphuric acid, again precipitated 
yammonia. The mixed oxyds were ignited, weighed, a 
fused with carbonate.of soda and nitre. From the solution in 
12°567 per cent.; mean = 12-599. 
The results were the following; in calculating the proportion 
of oxygen from the second analysis, the amount ‘of iron and 
chromium found in the other analysis was deducted from the 
Jot amount of the peroxyds, and the remainder assumed to be 
alumina. : 
1. il. Oxygen in I. In I. Mean. 
Si 81344-3178 16-284 16518 1640 
AL 17-467 8164 ) 
Fe 8-855 { son 1/156 9'848-1-156 9°709 978 
€r 1-686 052 0528 
Mg 33-44 33°64 13°376 13-456 13°42 
H 12599 19599 11:19 11-19 11-19 
100391 100°729 
Ratio between the oxygen of the silica, peroxyds, magnesia 
and water =1-677: 1: 1-372: 1:144 or 15:9: 12: 10 nearly. 
Mg* Sit+38 Si-oMg H, 
or 2Mg* Si+3% Si;+3Mg* H®, 
to the latter of which Rammelsberg gives the preference. ; 
According to Gerhardt’s theory, who considers the protoxyd 
peroxyds and water as replacing one another, this will come 
under that class of minerals, in which the oxygen of the silica 
is to that of the other constituents in the proportion of 1 to 2. 
Chemically considered, the only difference between the Clino- 
chlore examined and the ordinary chlorite appears to consist 1n 
the fact that the former contains chromium. It is, however, 
as has been shown by Mr. Blake, widely different in its optical 
Properties, STA aa he: at, ee Sea # 
