GEOLOGY. 227 



ORIGIN OF MOUNTAINS AND VALLEYS. 



Mr. A. Geikie, in a lecture at Dundee, in September, 1867, 

 alluded to the popular idea which refers mountains and valleys to 

 great convulsions, throwing up huge masses of matter and form- 

 ing vast chasms between. The arguments which he considers con- 

 clusive against this theory, as exhibited in the geological structure 

 of Scotland, he arranged under three heads. 1. While the hills 

 and uplands consist for the most part of hard rocks, the broad val- 

 leys are generally found on the soft rocks. In the highlands, for 

 example, the formations are mostly hard and crystalline metamor- 

 phosed rocks, while the lowlands, which run along their edges, 

 are of red sandstone and other soft rocks, the distinction between 

 the two being strikingly marked by the physical configuration. 

 2. The hills and mountains are not due to corrugations of the 

 earth's crust, nor to the form assumed by melted rock when forced 

 from beneath to the surface, as the mountains lie in the troughs, 

 while valleys are found where, if the popular theory were true, 

 mountains ought to be. Volcanic action cannot account for the 

 arrangement of the rocks, which must owe their form to some 

 general agency affecting all alike. 3. Valleys are found to run 

 across faults at all angles, and to have no relation to them what- 

 ever, and their systems are altogether inconsistent with the idea 

 that they were due to any subterranean causes. He considers 

 the present outlines of Scotland as having resulted mainly from 

 denudation, modified by local peculiarities, the agents in this 

 extensive process having been the sea, the atmosphere, rain, 

 frost, rivers-, glacier-ice, etc. ; the shaping of the land depending, 

 not on primeval terrestrial convulsions, but on the slow and silent 

 progress of the same agencies of waste which are at present 

 changing the outlines of the country. 



COURSE OF RIVERS. 



M. Babinet stated before the French Academy, as a general 

 rule, that rivers always tend to turn to the right, and consequently 

 to deposit toward the left their alluvium. M. Leymerie (" Comptes 

 Rendus," May 27, 1867), confirms this opinion by observations in 

 the valleys of the Garonne and the Tarn, and also in the smaller 

 valleys of the Pyrenees. It is evident that the force which pro- 

 duced this tendency to the left in quaternary periods must have 

 had considerable energy, and its study cannot fail to be of great 

 geological interest. 



GEOLOGICAL RELATIONS OF THE MASTODON AND FOSSIL 

 ELEPHANT OF NORTH AMERICA. 



Prof. Hall, at the meeting of the " American Association for the 

 Advancement of Science," at Burlington, Vt., in August, 1867, 

 began by remarking upon the general opinion at first popularly 

 expressed and generally adopted by geologists, that the mastodon 

 had lived during the present epoch, and that the skeletons or 



