102 A CENTURY OF SCIENCE 



the strand-lines of to-day, and those made fifty years ago 

 have to be revised again and again if they are to be of 

 value to the mariner and merchant. Therefore in our 

 future paleogeographic maps the tendency must ever be 

 toward smaller amounts of geologic time, if we are to 

 show the actual relation of water to land and the move- 

 ments of the periodic floodings. Moreover, the ancient 

 shore lines are all more or less hypothetic and are drawn 

 in straight or sweeping curves, unlike modern strands 

 with their bays, deltas, and headlands, and the ancient 

 lands are featureless plains. We must also pay more 

 attention to the distribution of brackish- and fresh- water 

 deposits. The periodically rising mountains will be the 

 first topographic features to be shown upon the ancient 

 lands, and then more and more of the drainage and the 

 general climatic conditions must be portrayed. In the 

 seas, depth, temperature, and currents are yet to be 

 deciphered. Finally, other base maps than those of the 

 geography of to-day will have to be made, allowing for 

 the compression of the mountainous areas, if we are to 

 show the true geographic configurations of the lands and 

 seas of any given geologic time. 



Paleometeorolot/y. 



In accordance with the Laplacian theory, announced at 

 the beginning of the nineteenth century, all of the older 

 geologists held that the earth began as a hot star, and 

 that in the course of time it slowly cooled and finally 

 attained its present zonal cold to tropical climatic condi- 

 tions. That the earth had very recently passed through 

 a much colder climate, a glacial one, came into general 

 acceptance only during the latter half of the previous 

 century. 



Rise. Our knowledge of glacial climates had its origin 

 in the Alps, that wonderland of mountains and glaciers. 

 The rise of this knowledge in the Alps is told in a charm- 

 ing and detailed manner by that erratic French- 

 American geologist, Jules Marcou (1824-1898), in his 

 Life, Letters, and Works of Louis Agassiz, 1896. He 

 relates that the Alpine chamois hunter Perraudin in 1815 

 directed the attention of the engineer De Charpentier to 

 the fact "that the large boulders perched on the sides of 



