205 
Mr. Gregor on a native Arseniate of Lead. 
of this paper, is an arseniat of lead, and that if we state that 
the relative proportion of the constituent parts of it are in one 
hundred, as follows, we shall not be far from the truth : 
Oxide of lead 
69.76 
Arsenic acid 
26,40 
Muriatic acid - 
1.58 
The silica and the oxide of iron, which account for a portion 
of the loss, and the alumina and copper which are sometimes 
found in an analysis of this fossil, I do not conceive to be es- 
sential to it. 
The existence of a minute portion of muriatic acid as a con- 
stant ingredient of it, is a curious fact : and it is still more 
curious, when we consider it in connexion with the analogy, 
that in this particular it maintains with the natural phosphats 
of lead. 
Creed, March x, 1809. 
E e 
MDCCCIX. 
