34 WORLD-MAKING 



This change may have amounted since the beginning of 

 Mesozoic time to one-third of its whole present width, which 

 would place the line of the coast ranges about two degrees of 

 longitude farther west." Here we have evidence that a tract 

 of country 400 miles wide and consisting largely of mountain 

 ranges and table-lands, has been crushed bodily back over two 

 degrees of longitude ; and this applies not to British Columbia 

 merely, but to the whole west coast from Alaska to Chili. 

 Yet we know that any contraction of the earth's nucleus can 

 crumple up only a very thin superficial crust, which in this 

 case must have slid over the pasty mass below. 1 Let it 

 be observed, however, that the whole lateral pressure of vast 

 areas has been condensed into very narrow lines. Nothing, I 

 think, can more forcibly show the enormous pressure to which 

 the edges of the continents have been exposed, and at the 

 same time the great sinking of the hard and resisting ocean- 

 beds. Complex and difficult to calculate though these move- 

 ments of plication are, they are more intelligible than the 

 apparently regular pulsations of the flat continental areas, 

 whereby they have alternately been below and above the 

 waters, and which must have depended on somewhat regularly 

 recurring causes, connected either with the secular cooling of 

 the earth or with the gradual retardation of its rotation, or with 

 both. There is, however, good reason to believe that the suc- 

 cessive subsidences alternated with the movements of plication, 

 and depended on upward bendings of the ocean floor, and 

 also on the gradual slackening of the rotation of the earth. 

 Throughout these changes, each successive elevation exposed 

 the rocks for long ages to the decomposing influence of the 

 atmosphere. Each submergence swept away and deposited as 



1 This view is quite consistent with the practical solidity of the earth, 

 and with the action of local expansion by heat, of settlement of areas 

 overloaded with sediment, and of downward sliding of beds. This we 

 shall see in the sequel. 



