JS4 STRUCTURAL GEOLOGY. 



In disintegration, therefore, we have an intricate plexus of forces acting 

 on an intricate plexus of matter. 



Now, so far as disintegration depends on the forces of heat, crystalli- 

 zation, and chemical change, the climate of the region is involved, aridity 

 being contrasted wi,th humidity, heat with cold, and great changes in either 

 factor of climate promote disintegration ; and so far as disintegration de- 

 pends on gravity, the declivity of the surface exposed to degradation is in- 

 volved, and a breaking up of the general declivity into greater and lesser 

 slopes, promotes disintegration. We may, therefore, discuss the dynamics of 

 disintegration as conditions of climate and declivity, and hence we may 

 consider the factors of disintegration to be petrology, climate and declivity, 

 and affirm that if the rate of transportation is sufficient to allow the forces 

 of disintegration to act to their fullest extent, the rate of disintegration will 

 depend on the heterogeneity of the rocks, heterogeneity of climate, and 

 heterogeneity of declivity. 



TRANSPORTATION. 



Gravity is the force acting in transportation. It acts directly in trans- 

 porting masses which fall from ledges and cliffs, and indirectly through the 

 agency of water. In this indirect method there are two sources for the 

 mechanical motion involved in the process: the one is the force of gravity 

 inhering in the water, which is the vehicle of transportation, the other the" 

 force of gravity inhering in the rocks transported. Let us call the latter 

 rock power, the former water power, and the rock material transported, load. 



It is manifest that if the rocks on disintegration were in a fluid state, 

 their owrrgravity would transport them. All of the rock material which is 

 dissolved is placed in this condition, and its own gravity is the force which 

 transports it; it does not float on the water, but behaves as an integral part 

 of it, and with it obeys the laws of hydrodynamics. In this case the water 

 is not the agent of transportation, but only the agent of disintegration. 



When the rocks are disintegrated mechanically the water is properly 

 the vehicle of transportation, and we have two cases, the one in which the 

 load is driven by the water, the other in which it is floated on the water. 

 When the transported matter is driven by the water along the bottom of the 



