I 
327 
In addition to the proofs, already adduced, of the solubility of 
silex in water, we may notice the circumstance of its having been 
found, in the proportion of 14 grains to 20 ounces, of the water 
collected in the cavities of basaltic columns. Its having circulated 
in the vessels of the animal body, and having been separated by 
the vessels of secretory organs ; and thus forming, though rarely, a 
part of the human urinary calculus, may also be regarded as evidence 
of some weight. But its presence in different plants affords still 
more powerful proof of its solubility, since we cannot conceive 
its absorption, its transportation through the substance, and lastly, 
its deposition in certain parts of plants, but in a state of actual 
solution in the water, with which the plant is nourished. Its pre- 
sence in the ashes of plants is well known. Rumphius relates^, 
that in the island of Celebes, near Macassar, stones are frequently 
found naturally formed in the wood and fruits of different trees : 
and that they are worn by the natives, being supposed by them 
to possess extraordinary powers; particularly that of defending 
them from the injuries of any weapon. These, however, will not, 
alone, afford us any considerable support; since, although the 
learned author describes them as Jlint-like stones, he mentions that 
they do not give sparks, and that they effervesce on being placed 
in an acid liquor. Mr. Macie has, however, found a pebble in the 
joint of a Bamboo cane, which was so hard as to allow it to cut 
glass f. Mr. Davy has ascertained most clearly, that flint enters 
into the composition of the epidermis of bonnet-cane, and indeed, 
of all cane of this kind. He found that when pieces of this kind 
of cane were rubbed together, strong sparks of white light were 
produced ; and that, when forcibly struck together, the sparks were 
as vivid as those from a gun-lock. The cause of this was ascer- 
tained beyond all doubt, by his finding that 22 grains of the epi- 
* D’Amboinsche Rariteit-Kamer. Ill Bock. LXVIII Hoofsdeel. 
f Philosophical Transactions, 1791, p. 385. 
