THE ADIRONDACK MOUNTAINS 9 



Geography deals with the distribution of the earth's physical 

 features, in their relation to one another, to the life of sea and 

 land and human life and culture. It is the present and outward 

 expression of geological effects. The terms geography and geology 

 are thus here used in the sense that the latter includes the former, 

 as the cause includes the effect. 



" The great lesson taught by the study of the outer crust is that 

 the earth-mother, like her children, has attained her present form 

 through ceaseless change, which marks the pulse of life and which 

 shall cease only when her internal forces slumber and the cloudy 

 air and surf -bound ocean no more are moving garments. The 

 flowing landscapes of geologic time may be likened to a kineto- 

 scopic panorama. The scenes transform from age to age, as from 

 act to act ; seas and plains and mountains of different types follow 

 and replace each other through time, as the traveler sees them 

 succeed each other in space. At times the drama hastens and 

 unusual rapidity of geologic action has in fact marked those epochs 

 since man has been a spectator upon the earth. Science demon- 

 strates that mountains are transitory forms, but the eye of man 

 through all his lifetime sees no change, and his reason is appalled 

 at the conception of a duration so vast that the milleniums of 

 written history have not accomplished the shifting of even one of 

 the fleeting views which blend into the moving picture." ^ 



All the rocks of the earth's crust may be divided into three great 

 classes : igneous, sedimentary and nietamorphic. 



Igneous rocks comprise all those which have ever been in a 

 molten condition, and of these we have the volcanic rocks (for 

 example, lavas), which have cooled at or near the surface: pliitonic 

 rocks (for example, granites), which have cooled in great masses 

 at considerable depths below the surface ; and the dike rocks which, 

 when molten, have been forced into fissures in the earth's crust 

 and there cooled. 



Sedimentary rocks comprise all those which have been deposited 

 under water, except some wind-blown deposits, and they are nearly 

 always arranged in layers (stratified). Such rocks are called 

 strata. They may be of mechanical origin such as clay or. mud 

 which hardens to shale; sand, which consolidates into sandstone: 

 and gravel, which when cemented becomes coiiglonicrate. They 

 may be of organic origin such as limestone, most of which is formed 

 by the accumulation of calcareous shells; flint and chert, which 



1 Joseph Barrel!. Central Connecticut in the Geologic Past, p. 1-2. 



