130 Scientifie Intelligence. 
These formulas belong to a single system or natural Group, and ex- 
hibit ina simple manner the relations of the species. Chloritoid and 
margarite are often associated together with corundum. a 
he second formula of Chloritoid corresponds to a recent analysis 
by Prof. von Kobell of a specimen from Bregratten, in the Tyrol, and 
to that by Dr. J. L. Smith of Asia Minor specimens. 
he water is not regarded as a base in the above, excepting in the 
margarite. This independent relation of water is illustrated in 
other crystallized hydrous silicates. Thus Pectolite, has the crystal. 
line form of hornblende; and excluding the water, its formula. So 
also Laumonite has in a similar manner the form and formula of 
Pyroxene, and in fact it isa hydrous Spodumene. Dioptase and Py- 
rosmalite, likewise, have the form and formula of Beryl! and Eudialyte, 
as shown on page 211, vol. xvii, of this Journal; Tritomite the form 
and formula of garnet; while Analcime is a hydrous Leucite, and 
Iitnerite essentially a hydrous Sodalite. ‘These are some of the exam 
ples among minerals, which show through homceomorphism, that the 
water in hydrous silicates is sometimes not a base. re 
In other cases, the water must be included among the bases : and 
this may be the fact with Apophyllite. The formula (Ga, K) 54-8 
(Rose) gives 3 per cent. too little of silica. But taking the exaet rallo 
afforded by the analyses, as deduced by Berzelius, and making part of 
the water basic, we arrive at the formula k Si2--2% = Silica 52°7, lime 
2°60, potash 4:4, water 16:7, in which R® corresponds to Ga, KH ™ 
the proportions 8:1:6. Datholite is a less doubtful example, givilé 
nearly the form and formula of Sphene af: 
It will be observed, that in most of the species following Pyroselerlé 
A, if the oxygen of the water be added to that of the bases (see table, 
. 128), its ratio to that of the Silica is then 2:1, on which ground, if 
the water be basic, the general formula of these species would be 
Vv 
third, of 1: 1. The analysis gives more exactly 4Na and 1403 
thence the oxygen of the silica is to that of the other ingredients ® 
1; 1, giving the general formula (R3, Zr, Ni) $i, in which i: Br: Re=1:3:4 
and affording the special formula 6R? Si+ 3%r Si+ NiSi, or (R? + 
+758) Si = Silica 31-2, niobie acid 14-3, zirconia 18-9, lime 27 
soda 8: 
Keilhauite.—The formula of this mineral, according to Erdmann, 7 
30a* Sit + BSi+ is, which contains three members with the widely 
unlike ratios 1: 2,1:1,1:6. E : 
make 
appears to be a silicate analogous to Sphene, with the general 
(#) Si? or (8, #) Si, 3 | 
ke a peroxyd if combined with the 7. Consequenti Keilhauil@ 

