Geology and Mineralogy. 139 



the consequent transfer of weight, brought about the mountain- 

 building disturbances and thus served to determine the form and 

 in part the elevation of the fold. 



The history of the peninsula of Florida, the promontory of 

 Yucatan and the Cincinnati axis appear to give support to this 

 view as to the relation of mountains and continents. (Author's 

 abstract.) 



3. Phenomena of beach and dune sands. 



The remarkable endurance of beach sands to the blows which 

 are inflicted by the waves is to be explained by the fact that 

 when mineral matter attains a certain state of division being 

 thoroughly wet, a film of water is usually held between the adja- 

 cent grains which serves to keep the surfaces apart and thus, 

 in a great degree, prevents abrasive action. Thus, while pebbles 

 wear rapidly in the mill of the surf, sand is very little worn. 



The effect of sea-weeds in bringing pebbles and sand into the 

 beaches is very great : this is accomplished by the floating action 

 of these plants on the objects to which they become attached in 

 the shallow water near the shore. 



The effect of floating pumice which becomes stranded along 

 the Atlantic coast is, at certain points, noticeable; but the 

 enquiries as to the value of the contribution have been retarded 

 by the difficulty which has been found in determining in a ready 

 way the difference between certain forms of furnace slag from 

 steamship boilers and true volcanic materials. 



The movement of dune sands is to a great extent made pos- 

 sible by the fact that these accumulations of sand rarely 

 become wet through, except it may be during the winter season. 

 A rain-fall of an half an inch will in general moisten the sands to 

 the depth of not over three fourths of an inch. The water flows 

 laterally to the center of the depressions and there only finds a 

 passage to the deeper parts of the dune. The result being that 

 in a short time the materials are dry enough to be set in motion 

 by the wind. 



The large amount of fine dust developed in dune sands, which 

 have been some time stable, shows the rapidity with which the 

 processes of decomposition of their materials advance. (Author's 

 abstract.) 



Wm. B. Scott discussed the Lacustrine Tertiary formations 

 of the West and gave the paleontological reasons for separating 

 the Paloduro beds from the Loup Fork proper. 



The classification of the Neocene formations (fresh water) of 

 the United States, proposed as the result of his latest studies, is 

 given in the following table (first published in Princeton College 

 Bulletin, vol. v, Nov., 1893, p. 84) : 



