258 PROGRESS OF SCIENCE IN THE CENTURY. 



on the crust by the contraction of the nucleus, and 

 studied these with deeper analysis than heretofore, 

 laying special emphasis on the horizontal lateral 

 pressures involved in the shrinkage. N. S. Shaler 

 in 1866 had used the contraction theory to explain 

 the origin of continents as well as mountain chains, 

 and Le Conte was also closely associated with 

 Dana's work. 



A new chapter begins with the work of Edouard 

 Suess. " A small book, published in 1875 under 

 the title, The Origin of the Alps, contained in 

 clear-cut outlines a wealth of new ideas ; it came 

 like vivifying rain on the dry ground." * This was a 

 preliminary suggestion of the author's famous 

 Antlitz der Erde (1897). In the preface to the 

 French translation of this geological masterpiece, 

 Marcel Bertrand says : " The creation of a science, 

 like that of a world, demands more than a day; but 

 when our successors come to write the history of 

 our science, they will say, I am persuaded, that the 

 work of Suess marks the end of the first day, when 

 light first shone." 



No one could give a summary of Gegenbaur's 

 Comparative Anatomy, and yet it is one of the zoolog- 

 ical milestones. The same must be said in regard 

 to the work of Suess. It is a comparative anatomy 

 and comparative embryology of land-forms, unified 

 by an evolutionary idea; but how can it be sum- 

 marised ? 



The theory that continents or mountains are due 

 simply to a force working from below upwards is an 

 unworkable crudity, though it must be allowed that 

 the shrinkage of the crust from contraction of the 

 nucleus caused vertical as well as horizontal dislo- 

 * Zittel, p. 462. 



