It is now proposed to show that those conclusions are not
well founded; and that, in this case of calcedony and iron-ore, it could
not be upon the principle of stalactical concretion that the bodies now
in question had their forms.
The principle upon which calcareous substance is dissolved in water, and
made to concrete by the evaporation of the acid substance, or fixed
air by which it had been dissolved, is too well known to require any
explanation in this place; we are only to consider the sensible effects
of those operations of which we know so well the proper conditions.
There are just two distinct views under which we may consider all
stalactical concretions formed; these are the incrustation of
the calcareous substance concreting upon a foreign body, and the
incrustation of the same substance upon itself. By the first any manner
of shape may be formed, provided there be a solid body, upon the surface
of which the calcareous solution is made to pass. By the second, again,
we have various forms; but we know the principles upon which they had
been made. These are the shape and motions of the fluid which gives the
calcareous concretion.
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