ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxiu 



of Arts and Manufactures. In 1831, through the mfluence of Cuvier, 

 he was named Assistant Professor of Geology to the Faculty of 

 Sciences, and soon afterwards he was named Honorary Professor of 

 the same science. In this year also he was deputed to visit the 

 volcanic island which had then suddenly appeared in the Mediter- 

 ranean ; and, having thus had his attention directed to volcanic phse- 

 nomena, he proceeded to examine them in Sicily, near Naples, in 

 Auvergne, and the Vivarais, the result of which was, that he an- 

 nounced himself an opponent of the views of Von Buch, regarding 

 craters of elevation, and expressed his belief that in Vesuvius, Etna, 

 Mont Dore, and the Cautal, the cones were merely produced by accu- 

 mulations proceeding from successive eruptions of ashes and of lava 

 streams. This abandonment of what had been his own previous 

 opinions, he spoke feelingly of as a necessary sacrifice to what he 

 considered truth, as he always entertained a high respect for Von 

 Buch. In like manner he was opposed to Elie de Beaumont, on his 

 theory of the elevation of mountain chains, M. Prevost not ad- 

 mitting an expansive force within the earth's crust sufiicient to ele- 

 vate mountain masses, and ascribing such apparent elevation to the 

 gradual contraction of the nucleus, and to the cracking and conse- 

 quent sinking of the crust on the one side, whilst on the other it 

 necessarily rose, the disturbed portion moving as it were on an axis 

 or hinge. That elevation and depression are generally coincident in 

 any great movements of the earth's crust, few, I should imagine, can 

 have a doubt; but it is right to observe that a force capable of 

 raising a column of lava to the elevation of many thousand feet, 

 would be also sufficient to raise a mass of land, supposing that the 

 force of cohesion had been overcome and a fracture produced. 



The great characteristic, however, of all M. Prevost' s works was, 

 that, in accordance with the principles of his illustrious friend De 

 Blainville, he endeavoured to illustrate the past by the present, and 

 that he even laboured to prove that the causes or forces which we 

 now see in action are in their nature sufficiently powerful to have 

 produced all the effects observable on the examination of the records 

 of the past operations of nature, whether of a formative or of a 

 destructive character, — a theory which, under the appellation of " the 

 doctrine of recent causes," has become familiar to geologists from 

 the works, especially * The Principles of Geology,' published in 1832, 

 of Sir Charles Lyell, and of whom Prevost thus speaks : — " I felt that 

 to carry out effectually my researches on the shore of France, it 

 was necessary that I should visit England, and there study the 

 normal type of the secondary formations. In 1824, therefore, I 

 visited, with my friend Mr. Charles Lyell, whose works and geologi- 

 cal doctrines have since rendered his name so popular throughout 

 the world, a part of the south and north of England, Cornwall, and 

 almost all the shores of the Channel, from the Land's End to Brighton ; 

 I studied also a part of the coast and the Isle of Wight in company 

 with Dr. Fitton, so well known by his * consciencieux travaux.' " 

 M. Prevost also read before the Academy of Sciences, in 1845, a 

 memoir on the * Chronologic des Terrains et du Synchronisme des 



