GENERAL LAWS IX GEOLOGY. 537 



physical history of the region, the boundaries of its raised sea bottoms, 

 the shores of the great continent on which the mammoths lived, the 

 period when the gold oi-e was formed, and when the watershed of the 

 Ural chain was elevated.] 



CHAPTER IV. 

 ATTEMPTS TO DISCOVER GENERAL LAWS IN GEOLOGY. 



Sect. 1. General Geological Phenomena. 



"DESIDES thus noticing such features in the rocks of each country 

 *-* as were necessary to the identification of the strata, geologists 

 have had many other phenomena of the earth's surface and materials 

 presented to their notice ; and these they have, to a certain extent, 

 attempted to generalize, so as to obtain on this subject what we have 

 elsewhere termed the Laws of Phenomena, which are the best mate- 

 rials for physical theory. Without dwelling long upon these, we may 

 briefly note some of the most obvious. Thus it has been observed 

 that mountain ranges often consist of a ridge of subjacent rock, on 

 which lie, on each side, strata sloping from the ridge. Such a ridge 

 is an Anticlinal Line, a Mineralogical Axis. The sloping strata pre 

 sent their Escarpemcnts, or steep edges, to this axis. Again, in min- 

 ing countries, the Veins which contain the ore are usually a system 

 of parallel and nearly vertical partitions in the rock ; and these are, 

 in very many cases, intersected by another system of veins parallel to 

 each other and nearly perpendicular to the former. Rocky regions 

 are often intersected by Faults, or fissures interrupting the strata, in , 

 which the rock on one side the fissure appears to have been at first 

 continuous with that on the other, and shoved aside or up or down 

 after the fracture. Again, besides these larger fractures, rocks have 

 Joints, separations, or tendencies to separate in some directions ra- 

 ther than in others ; and a slaty Cleavage, in which the parallel sub- 

 divisions may be carried on, so as to produce laminae of indefinite 

 thinness. As an example of those laws of phenomena of which we 

 have spoken, we may instance the general law asserted by Prof. Seclg- 



