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X. Description of the Arseniates of Copper , and of Iron, from 
the County of Cornwall. By the Count de Bournon. Com- 
municated by the Right Hon. Sir Joseph Banks, Bart. K, B. 
P. R. S. 
Read February 19, 1801. 
SECTION I. 
ARSENIATES OF COPPER, 
The natural combination of the arsenic acid with copper, and 
the different aspects under which this combination appears, 
according to the proportions in which these two substances are 
united, were among those objects of mineralogy, respecting 
which our imperfect knowledge required the aid of study and 
observation. A new copper mine, lately worked, called Huel 
Gorland, in the parish of Gwennap, in the county of Cornwall, 
having, within the last two years, enriched the cabinets of 
London with some very fine specimens of these arseniates, I have 
been induced to pay particular attention to them ; and I offer the 
result of my observations to the Royal Society, as an acknow- 
ledgment of that gratitude which I and all Frenchmen, faithful 
to their king, ought to feel and profess to a country which has 
distinguished itself as the protector of honour and loyalty. 
Although there appears, according to some German authors, 
reason to think that arseniate of copper has been found in 
Silesia, its much greater abundance, as well as the various 
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