388 Miscellanies. 



Thus determined, the quantities of the constituents of this ore are, 



Sulphur, - - III. - - - 178-4 

 Arsenic, - - IV. - 414.4 



Iron, - - VI. - - - 329.4 



Cobalt, - - VI. - - - 64.5 



Derived from mortar, II. - - - 10.1 



996.8 



Loss, partly iron, 



3.2 



1000. 



As arsenic, when sulphur is present, combines, in preference, with 

 iron to form a binarseniuret, we therefore conclude that such a com- 

 pound exists in this ore, and this opinion derives some support from 

 the fact, that muriatic acid dissolves iron from the mineral, without 

 a trace of arsenic being thrown out of combination. 



By dividing the loss among all the constituents, its composition 

 may be thus expressed, in accordance with definite proportions. 



Binarseniuret of iron, - 571.3 



Sulphuret of iron, - 290.6 



Bisulphuret of cobalt, - - - - 136.5 



998.4 

 The employment of short trivial names in mineralogy having re- 

 ceived the sanction of the most eminent naturalists, I propose the 

 name of Danaite for this mineral, in honor of the late Professor 

 James F. Dana, to whose skill in minute chemical research, we are 

 indebted for our knowledge of the existence of cobalt in this mineral. 



Roxbury Laboratory, May 27, 1833. 



3. Note to remarks on the Guaco* — Since the remarks address- 

 ed to the Editor on this subject, the notice of the writer has been 

 directed, by him, to a paper in the Journal of the Royal Institution, 

 (for 1830,) touching the same plant; but it appears obvious that the 

 writer, (Dr. Hancock,) does not, in that paper, understand by the 

 name guaco, the same plant which has been sent from Mexico to 

 Philadelphia and of which a specimen was forwarded to Professor 

 Silliman. 



* This note came too late to be inserted In connexion with Prof. Johnson's com- 

 munication <m the Guaco. — Ed. 



