344 EARTHQUAKES. 



CHAPTEE XXI. 



EARTH OSCILLATIONS. 



Evidences of oscillation — Examples of oscillation — Temple of Jupiter 

 Serapis— Observations of Darwin— Causes of oscillation. 



Evidences of oscillation, — By earth oscillations are 

 meant those slow and quiet changes in the relative level 

 of the sea and land which geologists speak of as eleva- 

 tions or subsidences. These movements are especially 

 characteristic of volcanic and earthquake-shaken coun- 

 tries. 



As evidences of elevations we appeal to phenomena 

 like raised beaches, sea-worn caves, raised coral reefs, and 

 the remains of other dead organisms like barnacles, and 

 the borings of lithodomous shells in and on the rocks of 

 many coasts high above the level of the highest tides. 

 As a proof that subsidence has taken place, there is the 

 evidence afforded by submerged forests, the prolongation 

 of certain valleys beneath the bed of the ocean, the 

 formation of coral islands, the peculiar distribution of the 

 plants and animals which we find in many countries, and 

 the submergence of works of human construction. Inas- 

 much as these phenomena are discussed so fully in many 

 treatises on physical geology, the references to them here 

 will be made as brief as possible. Elevations and depres- 

 sions which have taken place at the time of large earth- 



