350 DYNAMICAL GEOLOGY. 



Disco Bay, near 69° N., to the Firth of Igaliko, 60° 43', the coast has been 

 sinking for four centuries past. Old buildings and islands have been sub- 

 merged ; and the inhabitants have had to put down new poles for their 

 boats, the old ones standing, Lyell observes, ''as silent witnesses of the 

 change." 



On the North American coast, south of Greenland, from Labrador to 

 New Jersey, it is supposed that similar changes are going on. G. H. Cook 

 concludes, from his observations, that a slow subsidence is in progress 

 along the coasts of New Jersey, Long Island, and Martha's Vineyard, and 

 has deduced, from the positions of buried stumps over large areas along 

 the New Jersey coast, a rate of two feet a century. According to A. Gesner 

 the land is rising at St. John, in New Brunswick ; sinking at the island of 

 Grand Manan ; rising on the coast opposite, at Bathurst ; sinking about the 

 head of the Bay of Fundy, where there are regions of stumps submerged 

 35 feet at high tide, and about Minas Basin, in Nova Scotia, except, perhaps, 

 on the south side. 



On page 149 the reasons are given for believing that coral reefs and 

 islands are proof of a slowly progressing svibsidence, as first suggested by 

 Darwin. On the physiographic chart, page 47, the line CCC, extending in an 

 easterly direction from the Pelews, divides coral islands from those not coral. 

 Over the area north of it, to the Hawaiian Islands, all the islands are atolls, 

 excepting the Marquesas and three or four of the Carolines. If, then, the 

 atolls are registers of subsidence, a vast area has partaken in it, — meas- 

 uring 6000 miles in length (a fourth of the earth's circumference), and 

 1000 to 2000 in breadth. Just south of the line there are extensive 

 coral reefs; north of it the atolls are large, but they diminish toward 

 the equator, and mostly disappear north of it ; and, as the smaller atolls 

 indicate the greater amount of subsidence, and the absence of islands 

 still more, the line AA may be regarded as the axial line of this great 

 Pacific subsidence. The amount 6f this subsidence may be inferred, from 

 the soundings near some of the islands, to be at least 3000 feet. But as 

 200 islands have disappeared, and it is probable that some among them were 

 at least as high as the average of existing high islands, the subsidence in 

 some parts cannot be less than 5000 feet. This sinking probably began in 

 the Tertiary era. 



During the progress of this subsidence, or since it ceased, there have been 

 many cases of isolated elevation. The following are some examples from 

 the Pacific: Oahu (Hawaiian Islands), 25 feet; Elizabeth Island, Paumotu 

 Archipelago, 80 feet ; Metia or Aurora, 250 feet ; Atiu, Hervey Group, 12 

 feet ; Mangaia, 300 feet ; Purutu, 150 feet ; Eua, Tonga Group, nearly 500 

 feet ; Vavau, 500 feet ; Savage Island, 100 feet ; Eota and Guam, of the 

 Ladrones, 600 -feet. More than 25 others have undergone some elevation. 

 Off the New Guinea coast, some atolls have been raised to a height of 300 

 or 400 feet, and a central basin 100 feet deep, with vertical walls around, 

 occupies the place of the old lagoon. 



