446 Notices of British and Foreign Memoirs. 
The minerals distinguished specifically under the names of labra- 
dorite, andesine, and oligoclase, are in reality only terms of a con- 
tinuous series. ‘Those to which we cannot assign a place in the 
system are only intermediate terms of this series, which, up to the 
present time, have not been studied in detail. Two rather rare 
minerals—namely, Hyalophane, which contains barytes, and Dan- 
burite, in which boracie acid has replaced the alumina—range them- 
selves equally in the group of feldspars. 
The isomorphous mixtures of orthoclase and albite, and that more 
complete of albite, anorthite, and danburite, as well as that between 
orthoclase and barytiferous feldspar, have the atomic constitution 
shown in the following table :— 
Gost WATTONE. CHSUEGAL VOELIT A sifvin CORBTONE 
Anorthite Ca? Al? Al? Sit O16] Oligoclase, Andesine, Labrado- 
Albite Nat Al? Siz SiO rite, &c. 
Adularia K? Al? Si? Sit O'...Orthoclase, Sanidine, &c. 
Feldspar (barytic) Ba? Al? Si? Sit 0% 
Danburite Cae B? Be Sit ou | Hyalophane. 
Perhaps it would be convenient to admit for the feldspars of 
ordinary composition only three genera, that could be subdivided 
according to the proportions in which the normal species are found 
mixed in them.—L’ Institut, June 1865.—J. M. 
IV. On ConsIDERABLE Deposits oF PHosPpHATE OF LIME AT 
CacerzEs, EstremapurA. By M. R. pe Luna. 
(eee deposits are very extensive, and occur on the line of rail- 
way from Estremadura to Portugal. The means of transport 
are very costly in comparison to that of similar deposits. The 
phosphate of lime attains a maximum of 85 per cent. in the for- 
mation of Montanches, six leagues from Caceres and eight leagues 
from Logrosan, and the minimum is about 50 per cent. M. Luna 
has also noticed a deposit containing 72 per cent. of Ca’P, extending 
over four square kilométres, about half an hour’s journey from 
Caceres. 
The last mines discovered at Montanches are as rich as those of 
Logrosan. The phosphate is found in the cretaceous strata, and in 
great abundance in the silicious bed; it presents a fibrous texture, 
and as the formations do not contain carbonate of lime, it is more 
readily attacked by sulphuric acid. 
Phosphate of Caceres. Maximum. Minimum. 
Residue insoluble in nitric acid . : . 47-02 91:05 
Water ; i F ‘ ; : . 3800 1:33 
Tribasic phosphate of lime. : 5 APO 50:10 
Oxide of iron, &c. &c., and loss . ; Sarco 1:55 
Montanches. 
Tribasic phosphate . : ; 5 . 85:03 
Carbonate of lime : : ‘ : 5 JKORSYS) 
Oxide of iron—silica . ‘ : ; 240 
Water 4 ; j : : : ee, 
Comptes Rendus.—J. M. 
