448 PHILOSOPHICAL TRANSACTIONS. [aNNO J76O. 



as Africa, and more or less throughout almost all Europe. By the Rev, John 



Michell, M. A. p. 566. 



Introduction. — It has been the general opinion of philosophers, that earth- 

 quakes owe their origin to some sudden explosion in the interior of the earth. 

 This opinion is agreeable to the phenomena which seem to point out some- 

 thing of that kind. The conjectures, however, of the cause of such an explo- 

 sion have not been yet sufficiently supported by facts ; nor have the more par- 

 ticular effects which will arise from it been traced out ; and the connection of 

 them with the phenomena explained. To do this is the intent of the following 

 pages , and the dreadful earthquake of the 1st of Nov. 1755 supplies us with 

 more * facts for this purpose than any other earthquake of which we have an 

 account. 



That these concussions should owe their origin to something in the air seems 

 very ill to correspond with the phenomena. This will sufficiently appear, as 

 those phenomena are hereafter recounted ; nor does there appear to be any such 

 certain and regular connection between earthquakes and the state of the air, 

 when they happen, as is supposed by those who hold this opinion. It is said, 

 for instance, that earthquakes always happen in calm still weather : but that this 

 is not always so may be seen in an account of the earthquakes in Sicily of ] 693, 

 (Phil. Trans. N° 207,) where we are told, " the south winds have blown very 

 much, which still have been impetuous in the most sensible earthquakes, and 

 the like has happened at other times." Other examples to the same purpose we 

 have in an account of the earthquakes that happened in New England in 1 727 

 and 1728 ; the author of which says, that he could neither observe any connec- 

 tion between the weather and the earthquakes, nor any prognostic of them ; for 

 that they happened alike in all kinds of weather, at all times of the tides, and 

 at all times of the moon. Phil. Trans. N° 409. If, however, it should still be 

 supposed, notwithstanding these instances to the contrary, that there is some 

 general connection between earthquakes and the weather, at the time when they 

 happen, yet surely it is far more probable that the air should be affi?cted by the 

 causes of earthquakes, than that the earth should be aftected in so extraordinary 

 a manner, and to so great a depth ; and that this, and all the other circum- 

 stances attending these motions, should be owing to some cause residing in 



the air. 



Let us then, rejecting this hypothesis, suppose that earthquakes have their 

 origin under ground, and we need not go far in search of a cause, whose real ex- 

 istence in nature we have evidence of, and which is capable of producing all the 

 appearances of these extraordinary motions. The cause I mean, says Mr. M. 



* See the 10th vol. of these Abridgments. 



