C *95 3 
XI. On a native Arseniate of Lead. By the Rev. William 
Gregor. Communicated by Charles Hatchett, Esq. F. R. S. 
Read April 13, 1809. 
I. 
That the oxide of lead and the arsenic acid, might be found 
in the state of natural combination, is a supposition highly 
probable, from the strong affinity which subsists between 
these two substances. But the existence of such a compound 
has not, as I conceive, hitherto been established by such proofs, 
as entitle it to be ranked amongst the decided cases of mjne- 
ralogical science. I trust, therefore, that the observations, 
which I have the honour of submitting to the Society, on a 
new* ore of lead lately discovered in the county of Cornwall, 
so justly celebrated as well for the variety as for the richness 
of its mineral productions, will not be deemed superfluous. 
This mineral was raised in the mine called Huel-Unity, a 
very rich copper mine, in the parish of Gwennap. According 
to the information with which I have been favoured by Mr. 
William Davey, a very intelligent and experienced miner in 
that district, it was found in a lode south of Huel-Unity prin- 
cipal lode, at the depth of fifty fathoms below the surface, 
* It is new at least to the miners in Cornwall ; nor was there, previously to this 
discovery, any ore resembling it to be found in that splendid collection of minerals, 
which my valuable friend Philip Rashleigh, Esq. has so liberally formed, and as 
liberally employed in the promotion of Science. 
