Theories of the Earth's Physical Evolution. 327 



the weakest? or wh}' the particular epoch of disturbance should 

 coincide with, or immediately follow, the epoch of deposit ? What- 

 ever may be the meaning of these correlations, it is quite certain 

 that they are not accidental ; and it cannot be for one moment 

 admitted that such a gratuitous assumption, as these supposed lines 

 of weakness, is any explanation of them at all. 



Calling attention to the extreme displacement seen, the author 

 remarks there is still no chaos. In New England and the Middle 

 States the beds preserve their positions as perfectly as when they 

 were deposited. However vast the disturbing force may have been, 

 we may well wonder at the gentleness and ease with which they 

 have been lifted up or let down. As if to remind us how destructive 

 the force might have been, we find here and there a few acres which 

 have unmistakably been subject to lateral thrusts, in consequence of 

 the sliding of a large mass down a steep incline, or some other local 

 cause, and the strata have "gone into 'pi.'" This preservation 

 of continuity suggests that the force which produced the movements 

 was a minimum force — that is, a force haying the smallest intensity 

 which is capable of producing the movement. But this is demon- 

 strably a system of forces acting upwards at the anticlinals, and 

 downwards at the synclinals. It is equally capable of demonstration 

 that, of all possible modes in which a force could be applied to 

 produce a fold, the horizontal or tangential application would 

 require the greatest intensity. It is the latter force which the con- 

 tractional hypothesis supplies ; and the probable result of it would 

 be, not flexures, but the annihilation of all traces of stratification. 

 It is a law of mechanics that tendencies to rupture increase with the 

 cubes of dimensions, while resistances to rupture increase only with 

 the squares. The masses under consideration are collectively of the 

 extent of states and empires ; the individuals are mountain ranges 

 and valley bottoms ; and their coherence in the presence of the 

 forces which are adequate to move them becomes, by virtue of the 

 foregoing law, a vanishing quantity. Such masses, under the action 

 of the supposed force, would be the merest rubble, and quite 

 incapable of preserving their integrity. The action has frequently 

 been illustrated by subjecting a pile of paper to compression edge- 

 wise. A closer analogy would be presented if the paper were 

 reduced to ashes or charcoal before applying the pressure. A better, 

 though far from an adequate one, may be found in the chaos pro- 

 duced in the Arctic regions, where a great ice-floe is driven upon a 

 rocky coast. 



Captain Dutton had intended to have adduced other objections to 

 the contractional hypothesis, depending on the arrangement of 

 mountain systems, their structure, and the figure of the earth itself. 

 But he considers the arguments above given sufficient to overthrow 

 the theory. He has no theory to put in the place of it ; but j^romises 

 in a future article to indicate a few conditions, to which any such 

 must conform, before it can claim even a conditional acceptance. 

 The importance of the subject, and the philosophical spirit in which 

 it is here treated, must be our excuse for the length of the above 



