192 
Ir was Resotvep,—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 
