DYNAMICAL GEOLOGY. 307 



youngest mountain-chains were pre-eminent for the large 

 I participation of volcanic rock in their composition, more 

 especially along marginal fault-lines. 



Dana's views on mountain-building were based chiefly on 

 the Appalachian Rocky Mountains, and were well adapted to 

 the geological relations in North America. They were 

 therefore widely accepted in that country. Many of the ideas 

 were criticised by his compatriots, and the healthy interest 

 awakened in the subject reacted favourably upon Dana's 

 concept, as it enabled the author to revise and improve certain 

 portions. Joseph le Conte was the most brilliant of Dana's 

 ; helpers in working out the evidences of horizontal components 

 of pressure in mountain-folding; Dana so frequently cited Le 

 Conte in his later publications that it is difficult to define the 

 individual merits of the two geologists. 



To the North American geologists undoubtedly belongs 

 the credit of founding the theory of horizontally-acting forces 

 and rock-folding upon an ample basis of observation. 



Shaler distinguished between the uprise of continents and 

 that of mountain-systems. Both were explicable upon the basis 

 of the earth's contraction; but whereas the continents had taken 

 origin from furrows which affected the whole thickness of the 

 earth's crust, the mountains only represent foldings in the 

 external parts of the crust which have served to relieve the 

 lateral pressures produced by the contraction of the deeper 

 horizons. 



The method of research followed by Professor Suess marks 

 the beginning of a new epoch in the questions of crust- 

 deformation. Two aspects appealed strongly to Professor 

 Suess, the tectonical problems presented by individual 

 mountain-chains, and the relation of all the mountain-systems 

 on the surface of the earth to the physical changes in progress 

 since the beginning of the earth's history. Since Elie de 

 Beaumont's misguided effort, no geologist had attacked the 

 question from its universal aspect, and the supreme scientific 

 success attained by the first volume of Das Antlitz der Erde, or 

 The Face of the Earth, by Professor Suess, was a tribute to a 

 work accomplished with the highest bibliographical skill and 

 literary finish, the fullest geological and geographical 

 knowledge, a convincing array of scientific facts that never 

 fail to suggest an endless reserve in the background, and 

 above all a calm, judicial, elevated tone of inquiry which the 



