42 . EEPORT — 1842. 



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. If during this oscillation we conceive the whole heaving 

 tract to be shoved bodily forward in the direction of the waves, the union of this 

 tangential with the vertical movements may explain the peculiar steepening of the 

 anterior side of each flexure, and successive similar operations might occasion under 

 folding or inversion. 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 Earthquake*. — The authors suppose all earthquakes to consist in oscillations 

 of the earth's crust propagated with extreme rapidity ; and they ascribe this move- 

 ment 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, and if accompanied by the formation of dykes. The 

 successive earthquakes of any region usually proceed from the same quarter of the 

 compass, as must have been the case with the movements which gave rise to the 

 parallelism of neighbouring anticlinal axes. In illustration of the power of producing 

 permanent lines of elevation which earthquakes have exhibited in modern times, 

 the authors instance specially the Ullah Bund, an elevated mound extending fifty 

 miles across the eastern arm of the Indus, which was the result of the great earthquake 

 ofCutchin 1819. 



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 arrested the further progress of the coal formation. 

 With one local exception, on the Hudson, the whole series seems to have been depo- 

 sited conformably,without any emergence of the land. That the elevation did not take 

 place at a later period, is shown by the undisturbed condition of the overlying beds, 

 proximately of the age of the European new red sandstone. The elevation of the chief 

 part of the great belt of metamorphic rocks on the S.E. side of the chain is referred 

 to the same great movement. In conclusion, the authors remark that an incompa- 

 rably greater change in the physical geography of North America, and perhaps of the 

 globe, seems to have occurred at the close of the carboniferous epoch than at any 

 previous or subsequent epoch ; and they consider these changes, and the effect pro- 

 duced by them on the organic world, as affording some of the highest subjects of geo- 

 logical investigation. 



On the Production of Sa?id Storms and Lacustrine Beds, by causes associated 

 with the North American Lakes. By ilie Rev. Mr. Schoolcraft. 



A residence of nearly twenty years in the country whose physical geography is 

 strongly marked by the North American Lakes, had impressed the author with the 

 opinion, that these lakes afford a very striking example of the power of geological 

 action possessed, at the present day, by large bodies of inland water. For more than 

 half the indicated period his location had been in the immediate vicinity of Lake 

 Superior, and the present remarks are confined chiefly to that member of the series. 



Lake Superior itself may be considered as occupying an interstice between the 

 most northerly portions of the great secondary and sedimentary formations of the 

 Mississippi valley and the crystalline rocks of British America ; and this ancient line 

 of junction may be followed, down its outlet, through the Straits of St. Mary's into 

 Lake Huron, and is continued along parts of its north and north-easterly shores, north 

 of the fossiliferous limestones of the Manatouline chain. 



The western and northern sections of this lake exhibit the strongest proofs of 

 ancient action and upheaval. A colossal dyke of trap appears to have crossed the 

 lake, at about two-thirds of its length from east to west. Admitting (what appears to 

 be very probable) that the vast bed of the lake west of this dyke was originally pro- 

 duced by the sinking down of the strata and the consequent elevation of its shores, 

 we may attribute to the same disturbing force the central breach and prostration of 



