720 LECTUUE LVII. 



into the sea; yet notwithstanding the frequency of such accidents, the in- 

 habitants had so strong a predilection for their native spot, that they refused 

 the offer of a safer situation for rebuilding their houses. 



Convulsions of these kinds must have very materially influenced the dis" 

 position of the strata of the earth, as well as the form of its surface; but it 

 is by no means fully determined how far such causes have been concerned, 

 or how far the effects are to be attributed to the intermediation of water only. 

 Mineralogists and geologists have been principally divided into two classes 

 with respect to their theories of the earth, some maintaining the Vulcanian, 

 and some the Neptunian hypothesis. It appears to be impossible to decide 

 with any certainty between these opposite opinions; nor is it perhaps of 

 much consequence for any purpose of practice, or even of science. The 

 Neptunians are certainly able to establish their own theory positively, and 

 to prove that the fluid parts of the earth and sea must have been very materi- 

 ally concerned in producing the changes which have happened to the solid 

 parts; but it may be difficult for them to confute the assertion, that heat, 

 whether caused by volcanos or otherwise, has also been a very powerful 

 agent in these operations, and in some cases the joint effects of heat and of 

 increased pressure appear to have been concerned, in giving to minerals of dif- 

 ferent kinds tlieir actual form; although on the whole it seems probable that 

 the operation of heat has been much more limited than that of aqueous solu- 

 tions and precipitations. Mr. Davy has also very justly inferred, from his 

 experiments with the battery of Volta, that the effects of the electricity ex- 

 cited by means of chemical changes within the earth, have probably been 

 very materially concerned in the gradual formation of a variety of mineral 

 productions. 



The arguments for establishing the general fact, that great convul 

 sions have actually happened to the earth, are too well known to require 

 minute examination : the variety of fossil substances, many of them ma- 

 rine productions, and some almost preserving a recent appearance, that are 

 found in mountains remote from the sea, are undeniable proofs that the 

 levels of the earth's surface must have undergone considerable changes; al- 

 though some philosophers are of opinion, that such of the primary mountains as 

 are above 6 or 7OO feet high, have never been wholly covered by the sea. It 

 is not at ail easy to explain the change of climate, which some of these cir- 

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