366 Reéxamination of American Minerais. 
We are in favor of regarding the latter as representing the true 
formula. 
If Danburite be examined in its relation to datholite, it will be 
found to differ from the latter in having just one half the number 
of atoms of lime minus three atoms of water. 
Cae Sit + Bs Siz +- sit= Datholite. 
\ Ca’ Sit + Bs Siz = Danburite. 
This mineral forms then the second natural borosilicate of lime. 
hydrofluoric acid ; which according to previous experiments was 
shown to consist of silicic and boracic acids. Three re petitions of 
the above experiment gave perfectly concordant results: in fact 
no more beautiful proof could have been had of the absence of all 
other bases but lime, in any very sensible quantity. Moreover 
the amount of lime thus indicated, agrees perfectly with that 
obtained by the direct method of analysis. 
The boracic acid was estimated by first ascertaining the exact 
amount of silica by a soda fusion, and then deducting this quan- 
tity from the entire loss of a given quantity of the mineral under 
the action of hydrofluoric acid. 
€ specimens examined were among the finest that have ever 
been found, and were procured by Mr. Brush at the locality. 
28. Carrollite, a Copper-Linnaite. 
This mineral oceurs at Finksburg, Carroll Co., Maryland, and 
was described as a new species by Mr. W. L. Faber.* He gave 
as its chemical composition, 
s Co Ni Cu Fe s Si 
2704 2850 § 1-50 3299 B81 1°82 214 
Formula 200 S +Cu?5S. 
Our attention was first called to this mineral from the unusual 
relation of the sulphur to the metals in its composition, it being 
* This Journal, 2d Series, vol. xiii, 418. 
