226 S. D. Hayes on a New Lead-Salt. 
now appears, é . 
reference to the successive faunz of Trilobites as established in 
Bohemia and the rest of Europe. ee 
For myself I can say, that no previously expressed opinion, 
nor any “artificial combinations of stratigraphy previously adopted 
by me, shall prevent me from meeting the question fairly and 
frankly. ave not sought a controversy on this point, but tt 18 
quite time that we should all agree that there is something of 
high interest and importance to be determined in regard to the 
limitation of the successive faunse of our older palaeozoic rocks. 
I am very truly yours, &c., 
JAMES HALL. 
Albany, N, Y., January 23, 1861. 
——_— 
Art. XX.—On a new Lead-Salt, corre onding to Cobalt Yellow; | 
. by S. D. Haygs, of Boston. 4 
Iy the ‘course of some investigations on the cobalto-cyanid 
compounds, I was obliged to use a quantity of cobalt yellow, 
the pi ment discovere by M. Saint Evre in 1852.* 
; po ; then by 
passing a current of deutoxyd of nitrogen (NO?) through the 
mass, the cobalt yellow is obtained; but the greater part of t 
NO? passes through, without being absorbed ; the experiment 
requires hours; and the amount of salt so obtained is very sm#! 
As the composition of this body is considered doubtful, # 
oceurred to ye that it might be made from peroxyd of nitroge! 
(hyponitric acid, NO*), and after a few trials, I obtained it by ™ 
* Annal. Ch. Phys., 3d series, xxxyiii, 177. 
