HISTORY OF GEOLOGY. 



geologists, \ve have here a daily example of the operation of some 

 powerful agent which belongs to geological dynamics ; and which, for 

 the purposes of the geological theorist, does the work of the earth- 

 quake upon a very large scale, without assuming its terrors. 



[2nd Ed.] [Examples of changes of level of large districts occurring 

 at periods when the country has been agitated by earthquakes are 

 well ascertained, as the rising of the coast of Chili in 1822, and the 

 subsidence of the district of Cutch, in the delta of the Indus, in 1819. 

 (Lyell, B. n. c. xv.) But the cases of more slow and tranquil move- 

 ment seem also to be established. The gradual secular rise of the 

 shore of the Baltic, mentioned in the text, has been confirmed by 

 subsequent investigation. It appears that the rate of elevation in- 

 creases from Stockholm, where it is only a few inches in a century, to 

 the North Cape, where it is several feet. It appears also that several 

 other regions are in a like state of secular change. The coast of 

 Greenland is sinking. (Lyell, B. u. c. xviii.) And the existence of 

 " raised beaches " along various coasts is now generally accepted 

 among geologists. Such beaches, anciently forming the margin of the 

 sea, but now far above it, exist in many places ; for instance, along a 

 great part of the Scotch coast ; and among the raised beaches of that 

 country we ought probably, with Mr. Darwin, to include the " parallel 

 roads " of Glenroy, the subject, in former days, of so much controversy 

 among geologists and antiquaries. 



Connected with the secular rise and fall of large portions of the 

 earth's surface, another agency which plays an important part in 

 Geological dynamics has been the subject of some bold yet singular- 

 ly persuasive speculations by Mr. Darwin. I speak of the formation 

 of Coral, and Coral Reefs. He says that the coral -building animal 

 works only at small and definite distances below the surface. How 

 then are we to account for the vast number of coral islands, rings, and 

 reefs, which are scattered over the Pacific and Indian Oceans I Can 

 we suppose that there are so many mountains, craters, and ridges, all 

 exactly within a few feet of the same height through this vast portion 

 of the globe's surface ? This is incredible. How then are we to 

 explain the facts ? Mr. Darwin replies, that if we suppose the land to 

 subside slowly beneath the sea, and at the same time suppose the 

 coralline zoophytes to go on building, so that their structure constantly 

 rises nearly to the surface of the water, we shall have the facts ex- 

 plained. A submerged island will produce a ring; a long coast, a 

 barrier reef; and so on. Mr. Darwin also notes other phenomena, as 



