200 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



in each locality. A number of geologists have upheld the 

 opinion of Lyell and Agassiz that loess was of lacustrine or 

 fluvio-glacial origin. Giimbel, in discussing the Bavarian 

 loess deposits, drew attention more especially to the effects of 

 intermittent inundations of land during the frequent oscilla- 

 tions in the retreat of the Alpine glaciers. Laspeyres, 

 Baltzer, De Lapparent, and others think that torrential rains 

 and other subaerial forms of water have assisted in the for- 

 mation of loess. 



B. Geological Action of Water Springs. Water takes 

 undoubtedly the first and most important place amongst the 

 epigene geological agents. Its chemical and mechanical 

 activities are partly destructive, partly reproductive. They 

 affect the whole surface, and have not only determined 

 the present conformation of our planet, but have also given 

 origin to a very considerable part of the rock-material of 

 the Earth's crust. 



The authors who have contributed most to our knowledge 

 regarding water circulating in the ground are Bischof, Para- 

 melle, Lersch, and Daubree. Gustav Bischof wrote the first 

 scientific account of springs, illustrating it with his own 

 numerous observations on the relations of the underground 

 water in the Rhine Valley, on the ascent of springs, on 

 Artesian wells, and subterranean water-courses. Many of the 

 examples cited by Bischof are now familiar in text-books of 

 geology and physical geography. L'Art de decouvrir les Sources, 

 a work written by Abbe Paramelle, and translated into 

 German by Cotta in 1856, contains excellent hints on 

 the methods of finding springs and underground water. 

 Paramelle was the most successful water-diviner that ever 

 lived ; France owes to him the disclosure of numerous 

 springs. In 1864 and 1865 B. M. Lersch published at 

 Berlin his books on the Chemistry and the Physics of Natural 

 Waters. His Hydro- Chemistry gives especial attention to the 

 therapeutic aspects; while in the Hydrophysics there is, in 

 addition to his own observations, a carefully collected and 

 accurate account of all springs previously mentioned in 

 literature. Although the arrangement of this work leaves 

 much to be desired, the fund of information which it contains 

 gives it permanent value as a book of reference. 



The most complete works on natural waters are those 



