39 
JLrt of making Gun-Flints. 
when struck, and the face of the fracture is humid, and 
as it were moist. 
Chemical analysis. 
Citizen Vanquelin examined 100 parts of silex pyro- 
machus of a brownish colour, and uniformly semi-trans- 
parent from the hills of La Hoche Guion. He mixed the 
mass with 400 grains of very pure potash, which by fu- 
sion in a silver crucible afforded a compound, which after 
cooling was diffused in water, and then super- saturated 
with muriatic acid. The very clear solution was evapo- 
rated to dryness, re-dissolved in water, and the silex thus 
saturated, and left upon the filter after being well washed, 
dried and ignited, weighed 97 grains. Ammonia was 
afterwards added to the clear liquid, where it produced 
a slight yellowish white precipitate, which after being 
well washed and dried weighed one grain, and was found 
to be a mixture of alumine and oxide of iron. The fluid 
separated from this small portion of iron and alumine, 
gave no other precipitate on the addition of carbonate of 
potash, and the waters used in the washing left no resi- 
due when they were evaporated to dryness. The result 
therefore was silex = 97 grains, alumine and oxide of 
iron = 1, loss = £, The author considers it to be a very 
remarkable fact, that the silex pyromachus should con- 
tain only silex and water, the alumine and iron being too 
small in quantity to be considered as essential to its com- 
position, or to influence its habitudes. Quartz also, from 
the analyses which have been made, appears to contain 
only silex ; yet the more he examines the two substances, 
the more he finds reason to suppose them essentially dif- 
ferent from each other ; since the one refuses to assume 
the crystalline form, and the other assumes it and be- 
comes clear, even in contact with the flint itself. The 
one appears to be incapable of admitting water into its 
composition, while the other constantly contains it until it 
