as I have feen them, made into flabs, &c. Marble (I mean the white kinds) has been thought to be a refult of fuch vaft beds of fhells, as we have formerly mentioned: these being, when in union with fome liquor, broken into very minute parts, having fettled, affume the hardness and appearance of ftone; the veins in which are fuch adventitious interpofitions of earth, as accompanied the hardening mass. The idea is probable, fince both marble and fhells burn into much the same kind of lime. Thus we fee, that though denser matters are fometimes found upon lighter; yet it may be accounted for, without abandoning the idea, of the generally increafing gravity of the terrene layers, according to their depth. But how denfe, and compact, and folid foever be the interior beds which compofe our globe, they are fubject to many viciffitudes, and to much violence; not only where fubterraneous fires ftruggle, till they open in fome dreadful volcano, controuled, in part at leaft, by the refiftance of fuch well combined ftrata; but when the tremulous earth heaves its diftreffed bofom, oppreffed by a power to which resistance is vain; which, perhaps, is augmented by the firmness of the ftrata around its feat, and which, in a lighter medium, were fooner diffipated. I confider pent-up fires as the caufes of EARTHQUAKES; that, when by any means these are vifited by other elements (water or air), they expand them beyond opposition, and force a vent. If fire be a fluid appertaining to the globe, no wonder earthquakes are most frequent where the fun's influence is most powerful; and if the electric fluid be be a modification of that original fluid, all obfervations (which are numerous) of electric phænomena and effects, are agreeable to the principle. Woodward afcribed earthquakes to a stoppage of waters below the earth's furface. Thefe being accumulated, and acted on by fires (which he fuppofes ftill deeper), both contribute to heave up the incumbent earth. This, he thinks, accounts for the lakes of water produced in earthquakes, as well as for the fires that fometimes burft from the earth's fur face upon thofe dreadful occafions. Others have fuppofed the earth itself the cause of its own convulfions: the roots or bafis of fome large tract being worn away, by a fluid underneath, the earth finking therein occafions a tremor of the adjacent parts, fometimes producing a ftrange rumbling noife, and fometimes inundations of water. Without determining, a subject which has employed, on various fchemes, the fentiments of thofe beft ftudied in natural causes, I fhall relate fomewhat of their effects, as communiwitneffes. cated by eye The greatest we find in antiquity, is that mentioned by Pliny, in which twelve cities in Afia Minor were fwallowed up in one night, of which we have a monument remaining. That A. D. 1693, whofe damages were chiefly in Sicily, was felt in Germany, France, and England; extending a circumference of two thousand fix hundred leagues; chiefly affecting the fea coafts and great rivers, and being more perceivable upon mountains than in valleys. as I have feen them, made into flabs, &c. Marble (I mean the white kinds) has been thought to be a result of such vaft beds of fhells, as we have formerly mentioned: these being, when in union with fome liquor, broken into very minute parts, having fettled, affume the hardness and appearance of ftone; the veins in which are fuch adventitious interpofitions of earth, as accompanied the hardening mafs. The idea is probable, fince both marble and fhells burn into much the fame kind of lime. Thus we fee, that though denfer matters are fometimes found upon lighter; yet it may be accounted for, without abandoning the idea, of the generally increafing gravity of the terrene layers, according to their depth. But how denfe, and compact, and folid foever be the interior beds which compofe our globe, they are fubject to many viciffitudes, and to much violence; not only where fubterraneous fires ftruggle, till they open in fome dreadful volcano, controuled, in part at least, by the refiftance of fuch well combined ftrata; but when the tremulous earth heaves its diftreffed bofom, oppreffed by a power to which refiftance is vain; which, perhaps, is augmented by the firmness of the ftrata around its feat, and which, in a lighter medium, were fooner diffipated. I confider pent-up fires as the caufes of EARTHQUAKES; that, when by any means thefe are vifited by other elements (water or air), they expand them beyond oppofition, and force a vent. If fire be a fluid appertaining to the globe, no wonder earthquakes are most frequent the fun's influence is moft powerful; and if the ele be a modification of that original fluid, all obfervations (which are numerous) of electric phænomena and effects, are agreeable to the principle. Woodward afcribed earthquakes to a stoppage of waters below the earth's furface. These being accumulated, and acted on by fires (which he supposes still deeper), both contribute to heave up the incumbent earth. This, he thinks, accounts for the lakes of water produced in earthquakes, as well as for the fires that fometimes burst from the earth's furface upon those dreadful occafions. Others have fuppofed the earth itself the caufe of its own convulfions: the roots or basis of some large tract being worn away, by a fluid underneath, the earth finking therein occafions a tremor of the adjacent parts, fometimes producing a ftrange rumbling nolfe, and fometimes inundations of water. Without determining, a fubject which has employed, on va rious fchemes, the fentiments of thofe beft fredied in natural caufes, I fhall relate fomewhat of their effects, as communicated by eye witneffes. The greatest we find in antiquity, is that mentioned Pliny, in which twelve cities in Afia Minor were fwallowed eg in one night, of which we have a monument remaichg That A. D. 1693, whose damages were chiefy was felt in Germany, France, and England; exto cumference of two thousand fix hundred leagues; fecting the sea coafts and great rivers, and big ceivable upon mounting than in valleys. C as I have feen them, made into flabs, &c. Marble (I mean the white kinds) has been thought to be a result of such vast beds of shells, as we have formerly mentioned: these being, when in union with fome liquor, broken into very minute parts, having fettled, affume the hardness and appearance of stone; the veins in which are fuch adventitious interpofitions of earth, as accompanied the hardening mafs. The idea is probable, fince both marble and shells burn into much the fame kind of lime. Thus we fee, that though denfer matters are fometimes found upon lighter; yet it may be accounted for, without abandoning the idea, of the generally increasing gravity of the terrene layers, according to their depth. But how denfe, and compact, and folid foever be the interior beds which compofe our globe, they are subject to many viciffitudes, and to much violence; not only where fubterraneous fires ftruggle, till they open in fome dreadful volcano, controuled, in part at least, by the refiftance of such well combined ftrata; but when the tremulous earth heaves its diftreffed bofom, oppreffed by a power to which refiftance is vain; which, perhaps, is augmented by the firmness of the ftrata around its feat, and which, in a lighter medium, were fooner diffipated. I confider pent-up fires as the caufes of EARTHQUAKES; that, when by any means these are vifited by other elements (water or air), they expand them beyond oppofition, and force a vent. If fire be a fluid appertaining to the globe, no wonder earthquakes are most frequent where the fun's influence is moft powerful; and if the electric fluid be |
