192 



It was Resolved, — That the Academy do concur in the 

 preceding opinion expressed by the Council. 



Mr. Robert Mallet completed the reading of his paper on 

 the " Mechanics of Earthquakes." 



The author pointed out the correspondence of his theory 

 with the actual velocity of earthquake-shocks, so far as these 

 have been observed, and by numerous quotations shewed how 

 completely his theory accounts for the complex phenomena 

 often detailed, and many of which have been heretofore inex- 

 plicable. 



He shewed that an exact knowledge of the velocity of 

 earthquake-waves passing under the bed of the ocean, would 

 enable us to ascertain, with considerable certainty, what the 

 geological formations are, which, constituting this bed, form 

 more than two-thirds the whole surface of our globe, which 

 hitherto has been a geological blank. He also indicated the 

 means of experimentally determining the velocity of waves of 

 elastic compression in the crust of the earth, and proposed the 

 establishment of geological observatories, both separate and in 

 connexion with the magnetic observatories scattered over the 

 face of the globe, for the purpose of registering and recording 

 with suitable instruments, all the motions of the water of 

 earthquake-waves which occur ; and he has shewn reason to 

 believe that these (though so small as to be inappreciable 

 without the aid of proper instruments) are much more fre- 

 quent than has been hitherto supposed ; in fact, Arago has 

 actually observed an earthquake-shock at his magnetic obser- 

 vatory at Paris, which was imperceptible there without the aid 

 of instruments, and the origin of which lay in the south of 

 France. 



Dr. Lloyd took this occasion to mention that he had fre- 

 quently observed certain abnormal movements of the magnets 

 in the Dublin Observatory, which, like that noticed by M. 

 Arago, and referred to by Mr. Mallet, he was inclined to 



