1886.] NEW YORK ACADEMY OF SCIENCES. 31 



its heat, would either contract bodily as a red-hot cannon ball 

 does, or by the more rapid cooling of the outer surface, that 

 would shrink faster than the interior, and crack in every direc- 

 tion ; a process just the opposite from that which we find re- 

 •corded in the earth's crust. 



But there are other evidences of the flexibility of the earth's 

 ■crust which are incompatible with the theory which ascribes to 

 it great thickness. (1.) The lines of volcanoes which crown 

 most great mountain chains are located along fissures which 

 seem to be continuous for thousands of miles, and there is appar- 

 ently good evidence that these fissures penetrate through the 

 entire thickness of the solid crust. Sometimes the volcanoes are 

 in simultaneous action for several hundreds of miles, and the 

 materials ejected, though showing mucli variety, are often identi- 

 cal: facts incomprehensible on any other supposition than that 

 they have been drawn from a common reservoir.' 



(2.) Along all the coast lines the evidences of local changes of 

 level now in progress, or included in the records of past time, 

 are so numerous and striking that the term terra firma seems 

 singularly ill-chosen ; for example, the shores of the Mediter- 

 ranean abound in evidences of local depressions or elevation, or 

 both, since it has been occupied by civilized man. Of these the 

 temple of Jupiter Serapis at Baiae is one of the most famous, 

 but by no means the only example. 



On our own continent, the southern portion of Greenland has 

 been gradually sinking for several hundred years; Labrador and 

 Newfoundland are rising; Prince Edward's Island and Cape 

 Breton, according to Gesner, have sunk many feet since they 

 were first occupied by the whites. In Nova Scotia the land is 

 rising ; in Northern Maine it is sinking, as also at Cape Cod and 

 Martha's Vineyard and on the shore of Long Island and New 

 Jersey. Here the subsidence has locally varied from two to 

 twelve feet during the last century. In the "West Indies, there 

 are many evidences of local change of level ; in some cases, of 

 elevation, others, of subsidence. In California, we find traces of 

 recent and local flexures of the coast which are very striking ; 

 at San Diego is an old beach strewn with shells which have not 

 yet'lost their colors, twenty feet above the present sea-level. At 

 San Pedro, the port of Los Angeles, the limestone rocks which 

 form the sea cliffs are bored by Pholas eighty feet above the 

 water ; on the south shore of San Pablo Bay, at a height of twenty 



' Darwin mentions (" Trans. Geol. Soc," March, 1838), that in the 

 Andes the volcanoes Osorno, in lat. 40° S., Concagua, in 32" S., and 

 Coseguina, in lat. 13° N., burst into eruption simultaneously on the 20th 

 January, 1835. The more remote of the three are 3,700 miles apart. 



