198 Mr. Howard's Experiments and Observations 
not allow me to trespass more on the liberality of Mr. Greville, 
than to detach a small portion. I found it of similar composition 
to that of the three preceding stones ; and the Count de Bour-non 
has already shewn the proportionate quantity of the attractable 
metal to be very considerable. 1 grains, left 2^ of extraneous 
earthy matter; and yielded, by the treatment with nitric acid 
and ammonia, 174- grains of oxide of iron. This would seem 
to induce an estimation of i\ of nickel in 14 grains, or about 
9 per cent. 
55 grains of the earthy part of the stone, by the analytical 
treatment of the two former, afforded, 
Silica 25 
Magnesia » 91- 
Oxide of iron - 23-J 
Oxide of nickel * - i|- 
59 b 
The unusual increase of weight in the result of the three last 
analyses, notwithstanding the entire loss of the sulphur in the 
pyrites, is obviously owing to the metallic state of the iron 
combined with the sulphur, as was shewn in a former instance. 
I have now concluded the chemical examination of these four 
extraordinary substances. It unfortunately differs from the ana- 
lysis made by the French Academicians, of the stone presented 
to them by the Abbe Bachelay, as well as from that made by 
Professor Barthold, of the stone of Ensisheim . It is at variance 
with that of the Academicians, inasmuch as they found neither 
magnesia nor nickel. It differs from that of Mr. Barthold, as 
he did not find nickel, but discovered some lime, with 17 per 
cent, of alumina. With regard to these differences, I have to 
submit to the chemical world, whether magnesia might not 
