On the other hand, he finds siliceous bodies variously concreted among
the solid strata of the earth; and, from this he concludes, that
siliceous substance has been both dissolved by water in the strata, and
also there again concreted and crystallised in having been separated
from the water. This is certainly what we all perceive; but we do not
all allow ourselves to draw such inconclusive inferences from our
premises. Notwithstanding the greatest accuracy of our observations,
quartz may be dissolvable in a minute degree by water, upon the surface
of this earth; and, all the appearances of siliceous bodies, in the
mineral regions, where we cannot immediately see the operation, may be
better explained by fusion than by aqueous solution.
But, from his chemical experiments, our author has conjectured that
there may be a phlogistic substance, by means of which the siliceous
earth is dissolved when in darkness; and that this solvent loses its
power, if exposed to the light of day. I have one observation to oppose
to this ingenious theory. Under deep black mosses, through which no ray
of light can penetrate, every condition for dissolving siliceous bodies
should be found, according to the supposition in question; neither will
sufficient time be found wanting, in those deep mosses, upon the summits
of our mountains; yet, examine the matter of fact? not the smallest
solution is to be perceived in the siliceous parts of the stones which
are found under those mosses, but every particle of iron is dissolved,
so that the surface of every stone is white, and nothing but the
siliceous earth of the feld-spar, and perhaps the argillaceous, is left.
Pages:
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62