106 Analyses of the Chrysoberyls from Haddam and Brazit. 
variety of the cymophane; but from its inferior hardness: 
and general chemical composition, | recognized it to be 
common beryl. 
For the earliest chemical information concerning the 
chrysoberyl, we are indebted to Professor Klaproth. He 
published his analysis of it in 1795,* and gave the follow- 
ing constituents of it, viz. alumina, 74.50; lime, 6. ; oxide 
of iron, 1.50; silica, 18.; loss, 3. erzelius presented 
us with a formula founded on this composition ;f but from 
his experiments with the blowpipe he was led to conclude 
that it contained no lime, and that it was a subsilicate of 
alumina.t In this he was apparently confirmed by Pro- 
fessor Thomson.§ who quotes Klaproth’s analysis, and 
states that he examined the mineral some years ago, but 
having accidentally lost his results, he was unable to pub- 
lish them. He observes, however, that the only constit- 
uents he found were alumina, silica, and oxide of iron. 
When I was about to prepare the communication which I 
have now the honor to lay before the Society, a more re- 
cent analysis of the chrysoberyl of Brazil, by M. Augustus 
Arfwedson, was observed, by me, in Tilloch’s Philosophi- 
cal Magazine.|| He confirmed the results of Professor 
Thomson and considered the chemical composition of this 
substance to be—silica, 18.73; and alumina, 81.43, with 
a trace of oxide of iron. 
The cymophane, from Haddam, was sent to M. Hauy 
by the late Dr. Bruce, in 1810, to have his opinion con- 
cerning its nature.** Previous to that period, the mine- 
ralogists in the United States supposed it to be corundum. 
The late celebrated crystallographer observes, ‘“‘La cy- 
mophane des Etats Unis a d’ abord eté prisé pour une va- 
rieté de corindon. Effectivement elle se rapproche de ce: 
* Beitrage, vol. i. p. 97. 
t Systeme de Mineralogie, p,219,—C4S+18A48S. 
} Essai de’ 1’ Emploi du Chalumeau, p. 325. 
$ Thomson’s Chemistry, vol. iii. p. 213. 
|| No. for November, 1823, p. 357. 
** Annales du Museum d’ Histoire Naturelle, tome xviii. p. 57- 
