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latory motion of the earth during earthquakes, they beheve that all 

 the grand ancient flexures of North America were produced at one 

 time, and at the termination of the carboniferous asra, up to which 

 period they were all beneath the sea, and consequently still in a 

 flexible condition. These sediments were, it is supposed, subjected 

 to flexures by the invasion from below of molten matter ; and the pe- 

 culiar and numerous convolutions are explained by calling itito play 

 an upheaving, wave-like oscillation, accompanied by a tangential or 

 lateral pressure upon flexible masses which reposed u^Jon a semifluid 

 matter. English geologists y>all recollect that, in our account of the 

 carbt)niferous strata of North Devon, Professor Sedgwick and my- 

 self distinctly referred their multitudinous flexures to lateral pres- 

 sure ; because in this case Ave had the eruptive wedge-like chain of 

 Dartmoor on one flank and the older sedimentary ridge of the North 

 Foreland and the Quantock Hills on the other, forming a resisting 

 buttress, between which the intervening strata might very vrell be 

 squeezed into their contorted shapes. In the American case lateral 

 pressure was, it appears, applied on one side only of the bent strata; 

 and hence the phaenomena described, appear to me to indicate sim- 

 ply a dying out in a certain direction of the disturbing powers. 



Admiring the positive geological results which have been derived 

 from the survey of Pennsylvania, I regret that the theoretical in- 

 ductions of the authors were suddenly brought before a body at 

 Manchester unacquainted with the country which the authors had 

 patiently worked out, and on which their reasoning was mainly 

 founded. Unprovided also with the remarkable maps which have 

 been prepared by Professor H. Rogers and his assistants, and with- 

 out diagrams to illustrate the mechanical principles it involved, the 

 geologists at Manchester could ill judge of the merits of the theory. 

 A better acquaintance with the facts as well as with the objects of 

 that memoir, induce me, however, to view it as a praiseworthy effort 

 to establish laws of phganomena regarding subterranean movements ; 

 from a careful survey of the actual positions and relations of the 

 masses moved in a definite but sufficiently extensive district. The 

 manner in which these laws are expressed is perfectly (it must be 

 admitted) in the spirit of inductive philosophy; and the intentions 

 of the authors in presenting them, was trvily stated to be " to call 

 the attention of British geologists to analogous pha^nomena, which 

 the authors think they detect in mutually parallel axes of some of 

 the most interesting districts of Great Britain and the Continent." 

 It is therefore my duty to invite your attention to the vieAts which 

 this communication embraces ; and whatever may be your conclu- 

 sions respecting tiie theory, to request you to bear in mind, that it 

 was suggested by a Avide and successful field-survey which is replete 

 with sound research, and that the niemoir Avas generoiisly confided 

 jto the friendly feelings of the geologists of England, 

 ^i. I would next adveft to the labours of Di% Dale Owen of Indiana, 

 who has presented this Society with a paper on the geology of 

 the Western States of North America. In this memoir Dr. Owen 

 comprises not only the results of his OAvn observations since 1834, 



