It is not meant to allege, that it is only upon the summit of a continent volcanos should appear.  Subterraneous fire has sometimes made its appearance in bursting from the bottom of the sea.  But, even in this last case, land was raised from the bottom of the sea, before the eruption made its exit into the atmosphere.  It must also be evident, that, in this case of the new island near Santorini, had the expansive power been retained, instead of being discharged, much more land might have been raised above the level of the ocean.

Now, the eruption of that elastic force through the bottom of the sea, may be considered as a waste of power in the operations of the globe, where the elevation of indurated strata is an object in the exertion of that power; whereas, in the centre of a continent sufficiently elevated above the level of the sea, the eruption of that fiery vapour calculated to elevate the land, while it may occasionally destroy the habitations of a few, provides for the security and quiet possession of the many.

In order to see the wisdom of this contrivance, let us consider the two extreme places at which this eruption of ignited matter may be performed.  These are, on the one hand, within a continent of land, and, on the other, at the bottom of the ocean.  In the one case, the free eruption of the expanding power should be permitted; because the purpose for which it had been calculated to exist has been accomplished.  In the other, again, the free eruption of that powerful matter should be repressed; because there is reserved for that power much of another operation in that place.  But, according to the wise constitution of things, this must necessarily happen.  The eruption of the fiery vapour from volcanos on the continent or land, is interrupted only occasionally, by the melted bodies flowing in the subterraneous chimney; whereas, at the bottom of the ocean, the contact of the water necessarily tends to close the orifice, by accumulating condensed matter upon the weakest place.

If this be a just theory of the natural operations of the globe, we shall have reason to expect, that great quantities of this melted matter, or fusible substance, may be found in form of lava, among the strata of the earth, where there are no visible marks of any volcano, or burning mountain, having existed.  Here, therefore, is an important point to be determined; for, if it shall appear that much of this melted matter, analogous to lava, has been forced to flow among the strata which had been formed at the bottom of the sea, and now are found forming dry land above its surface, it will be allowed, that we have discovered the secret operations of nature concocting future land, as well as those by which the present habitable earth had been produced from the bottom of the abyss.  Here, therefore, we shall at present rest the argument, with endeavouring to show that such is actually the case.

It appears from Cronstedt’s Mineralogy, that the rock-stone, called trap by the Swedes, the amygdaloides and the schwarts-stein of the Germans, are the same with the whin-stone of this country.  This is also fully confirmed by specimens from Sweden, sent me by my friend Dr Gahn.  Whatever, therefore, shall be ascertained with regard to our whin-stone, may be so far generalized or extended to the countries of Norway, Sweden, and Germany.