JOINT WORK OF AIR AND SEA 2<J 



of the land outlines of ancient days to be traceable in the 

 remote past. 



There is, however, a way in which sea shores, even those 

 of very ancient times, may be preserved and revealed to our 

 time. This occurs, where, in place of the land rising- in the 

 continental oscillations, it sinks, so that the shore line becomes 

 submerged. In this case, when the indices of the submerged 

 shore are not destroyed as they pass through the mill of the 

 surf, they may be buried beneath stratified deposits, which 

 may accumulate to any thickness. When the region is again 

 elevated and the rocks brought above sea level, erosion may 

 disclose to us the marks of an old shore line preserved in an 

 excellent shape for ready determination. 



It is well for tlie student to associate in his understanding 

 the joint work of marine and atmospheric agents in wearing 

 away the land. He will thus see, in his mind's eye, the two 

 great agents of degradation in their cooperative work, and he 

 will be prepared to interpret some of the most interesting 

 features which the continents exhibit. 



^.r::^JS 



The Cvens Mount Desert, Maine 



431753 



