570 Proceedings of the British Association, 



of fracture, produce violent pulsations on the surface of the fluid below, 

 This oscillatory movement would communicate a series of temporary 

 flexures to the overlying crust, which would be rendered permanent 

 by the intrusion of molten matter into the fractured strata originating 

 the tangential force by which the flexures received their peculiar 

 character before described. The authors do not deem it essential to 

 this explanation that, in the production of axes of elevation, the strata 

 should be permanently fractured to the surface. Fissures sufficient 

 for the escape of vast bodies of elastic vapour, might open and close 

 again superficially; and the strata may often be supported in their 

 new position by subterranean injections not visible on the surface. 



Identity of the Undulations which produced the Axes, with the wave-like 

 motion of the Earth in Earthquakes. — The authors suppose all earth- 

 quakes to consist in oscillations of the earth's crust propagated with 

 extreme rapidity ; and they ascribe this movement to a sudden change 

 of vertical pressure on the surface of an interior fluid mass, throwing it 

 into wave-like undulations, such as would produce permanent flexures 

 in the strata if more energetic, accompanied by the formation of dykes. 

 The successive earthquakes of any region usually proceed from the 

 same quarter, and this must also have been the case with the move- 

 ments which gave rise to the parallelism of contiguous anticlinal lines. 

 In illustration of the power of producing permanent lines of elevation 

 which earthquakes have exhibited in modern times, the authors in- 

 stance the Ullah Bund, an elevated mound extending 50 miles across 

 the eastern arm of the Indus, which was the result of the great earth- 

 quake of Cutch in 1819; and another case recorded in 'Darwin's 

 Journal of Travels in South America,' which a traveller described as a 

 line of elevation of the strata, crossing a small rivulet, and shown in 

 the fact that he found himself going down hill while ascending the dry 

 deserted channel. 



Date of the Appalachian Axes. — The authors describe the elevation 

 of this chain as simultaneous with the termination of the carboniferous 

 deposits of the United States, and as the cause which probably arrest- 

 ed the further progress of the coal formation. With one local excep- 

 tion, on the Hudson, the whole series seems to have been deposited 

 conformably, without any emergence of the land. That the elevation, 

 did not take place later, is shewn by the undisturbed condition of the 

 overlying beds, approximately of the age of the European new red 

 sandstone. The elevation of the chief part of the great belt of meta- 

 morphic rocks on the S.E. side of the chain is referred to the same 

 great movement. In conclusion, the authors remark that an incom- 



