570 THE JOURNAL OF GEOLOGY. 



elevation of the highest mountains. But still he seems uncertain 

 if it be enough. In fact, he declares that if it were not for another 

 factor yet unmentioned, he probably would never have brought 

 forward the theory at all. 



(9) This factor is re currency of the cause and accumulation of 

 the effects. And here the previous obscurity becomes intensified. 

 I have read and re-read this part without being able wholly to 

 understand him. He seems to think that when expansion had 

 produced elevation, the mountain thus formed would not come 

 down again by cooling and contraction ; but on the contrary would 

 wedge up by normal faulting and set i?i its elevated position. After- 

 ward, by new accumulation of heat, another elevation and setting 

 would take place and the mountain grow higher, and so on inde- 

 finitely, or until the store of heat is exhausted. Therefore he 

 characterizes his theory as that of "Alternate expansion and con- 

 traction" or again as that of " Cumulative recurre7it expansion." 



Such is a very brief, perhaps imperfect, but I hope fair out- 

 line of Reade's theory. It seems to me that there are fatal 

 objections to it. These I now state. 



Objections. — I. The first is i?iadequacy to account for the 

 enormous foldings 1 of the mountains especially when there is no 

 granite axis to fold back the strata. It is true that Mr. Reade 

 makes comparison between his own and the contractional theory 

 in this regard, and seems to show the much greater effectiveness 

 of his own. This may be true if we accept his premises and com- 

 pare equal areas in the two cases. But the contractional theory 

 draws from the whole circumference of the earth and accumulates the 

 effects on one line, while in Reade's theory the expansion is, of 

 course, very local. 



2. But the fatal objection is that brought forward by Davi- 

 son. It is this : sedimentation cannot, of course, increase the 

 sum of heat in the earth. Therefore the increased heat of the 

 sediments by rise of isogeotherms, must be taken from somewhere 

 else. Is it taken from below ? Then the radius below must con- 

 tract as much as the sediments expand and therefore there will 

 be no elevation. Is it taken from the containing sides ? Then 



