416 Theories of the Formation of Motmtains. 



reo-ions where we know that beds of sediraent are beino; formed 

 seems to confirm this view. {See this Journal, Vol. 1, pp. 194? 

 195. 



Professor Hall's Theory. 



Professor Hall's Theory appears to us to be closely related to 

 those of Rogers, Lyell, Buffon and Herschel. The fundamental 

 fact in the greater accumulation of sediment along the south 

 eastern side of the Appalachians than on the south western, as 

 evidenced by the thinning out of the strata in a westerly direc- 

 tion. This was pointed out by Rogers in 1842 and has also been 

 described at greater length in his recent extensive work. Pro- 

 fessor Hall after noticing these accumulations in detail, says : — 



''When these are spread along a belt of sea bottom, as origin- 

 ally is the line of the Appalachian chain, the first effect of this 

 great augmentation of matter would be to produce a yielding of 

 the earth's crust beneath, and a gradual subsidence will be the 

 consequence. We have evidence of this subsidence in the gra- 

 dual amount of material accumulated ; for we cannot suppose 

 that the sea has been originally as deep as the thickness of these 

 accumulations. On the contrary, the evidence from ripple-marks, 

 marine plants and other conditions, prove that the sea in which 

 these deposits have been successively made was at all times shal- 

 low, or of moderate depth. The accumulation, therefore, could 

 only have been made by a gradual or periodical subsidence of 

 the ocean bed ; and we may then inquire, what would be the re- 

 sult of such subsidence upon the accumulated stratified sediments 

 spread over the sea bottom ? 



*' The line of greatest depression would be along the line of 

 greatest accumulation, and in the direction of the thinning mar- 

 gins of the deposit the depression would be less. By this pro- 

 cess of subsidence, as the lower side becomes gradually curved, 

 there must follow as a consequence, rents and fractures upon that 

 side ; or the diminished width of surface above, caused by this 

 curving below, will produce wrinkles and foldings of the strata. 



" The sinking down of the mass produces a great synclinal axis, 

 and within this axis, whether on a large or small scale, will be 

 produced numerous smaller synclinal and anticlinal axes. And 

 the same is true of every synclinal axis, where the condition of 

 the beds is such as to admit of a careful examination. I hold, 

 therefore, that it is impossible to have any subsidence along a 



