the Revolutions wkic/i have takai place on the Globe. 253 



the contrary, wherever rocks of an age not older than that of 

 the green-sand or chalk, appear in the vicinity of any portion 

 of this system, they are either found at a dead level and 

 expanded from the neighbouring mountains into horizontal 

 planes, like the sea at the base of a lofty cliff; or if, since their 

 first deposit, they have undergone any great movement, it is 

 shown to have no relation to the bearing of the older ridges, 

 and to have been produced at a later period. 



From all these combined facts follow three important con- 

 sequences. ] St, That the whole system of parallel ridges, from 

 one end to the other, was elevated at the same period of time, 

 after the development of the oolitic series, and before the de- 

 position of the green-sand and chalk. 2ndly, That the action 

 of elevation was violent and of short continuance, for the in- 

 clined strata are shattered and contorted ; and between them 

 and the horizontal strata there is no intermediate gradation of 

 deposits. Srdly, That the period of elevation was followed by 

 an immediate change in many of the forms of organic life. 



VIII. System of Mont Visa. — The French Alps and the 

 S.W. extremity of the Jura, from the environs of Antibes 

 and Nice to those of Pont d'Ain and Lons-le-Saulnier, present 

 a series of crests and dislocations with a direction towards the 

 N.N.W., in which the older beds of the Wealden formation, 

 the green-sand, and the chalk, are upheaved as well as those 

 of the oolitic series. The pyramid of primitive rocks of 

 Mont Viso is traversed by enormous faults, which from their 

 direction evidently belong to this system of fractures. The 

 eastern crests of the Devolny, north from Gap, are composed 

 of the most ancient beds of the system of green-sand and chalk, 

 thrown up in the direction in question, and elevated more 

 than 4700 English feet above the level of the sea. At the 

 feet of these enormous escarpments, are horizontally deposited, 

 near the Col de Bayud, and at more than 2000 feet lower 

 down, those upper beds of the cretaceous system which are 

 distinguished from the rest by the presence of jSJummulites, 

 Cerithia^ Ampullaricc, and other shells, the genera of 

 which were long considered as not extending deeper in the 

 series than the tertiary rocks. Thus it was between the two 

 portions of that which is commonly termed the series of tlie 

 Wealtlen formation, green-sand, and chalk, that the beds of 

 the Mont Viso system have been upraised. 



IX. Pi/renco-Apcnnine System. — Professor Sedgwick pre- 

 sented a summary of this system, in his last Address to the 

 deological Society of London, and I must not omit to men- 

 tion that important parts of the whole evidence were added 

 by i'rofessor Sedgwick himself and Mr. Murchison, during 



their 



