ON THE NEW METALS. ^63 



Mr. Mabru found this variety at the foot of Puy-Saint- Where found, 

 Romain, below the plaster quarries of St. Maurice, about 

 ten miles south-east of Clermont, in the department of 

 Puy-de-Dome. Its gangue is a compact carbonate of lime 

 of a gray colour, mixed with a little argilc and oxide of 

 iron. The largest crystals I have observed, are about 

 18 mill., or 8 lines [7 lines Eng.] broad. In the same place Size, 

 is found equiaxal carbonate of lime without any modifi- 

 cation. 



VIL 



Second Letter on the Subject of the Nezo Metals. 

 Bij Mr. A. Combes. 



To Mr. .NICHOLSON. 

 SIR, 



As 



.S you have fcandidly admitted ia letter into your Journal, The q\iestio>i 

 in which your own statements (as it seems) are censured, '"'^^P^';^^^ '"^' 



■' \ y J torical docu- 



you will not, I trust, refuse a place to my reply to your ments. 

 observations *. It may be considered as presumption in an 

 obscure individual, to enter into the lists with a veteran in 

 science ; and this would be the case, were the question of 

 any other nature than merely concerning historical docu- 

 ments; upon these topics the mere man of leisure may have 

 an advantage over the man of business and genius; and to 

 refer to authorities requires no great intellectual exertion. 



I still maintain, in opposition to j^our opinion, for which Foiucroy's tes- 

 on all other occasions I have the highest respect, that the ^'^['^"y equivo* 

 true alkalis " were never long ago suspected to be metallic 

 oxjdes." 



You mention the testimony of Fourcroy, but the passage 

 to which you refer is undoubtedly equivocal. 



Mr, Fourcroysays, Systemc desCon, Chem H, pag. 196, 

 *' I'opinion sur la pretcndue nature meilalliquc do la Barite 

 ainsi que celle des autres bases salifiables surtout terreuses 

 pe sera au'une hypothese." Here " des autres" ought, 



* SceJourns^l, p. 231—4. 



