SUNSPOTS AND VOLCANIC AND SEISMIC PHENOMENA. 51 



("Geografi. Argentina's Tidligste Tilstand "; see "Frem," published 

 by "Det Nordiske Forlag," May 14th, 1899). Perhaps up to this 

 time remnants of a South Pacific continent may have existed, and 

 additional conditions may have obtained which were very favour- 

 able to keep up the heavy sedimentation with which the origin of 

 the Andes and the commencement of vulcanism in this region 

 were connected. On biological evidence alone, the German 

 naturalist Ochsenius puts the separation of Lake Titicaca from 

 the Pacific, and the elevation of the Bolivian plain in a compara- 

 tively recent geological period. (See "Geografi. I/ceoninger af 

 Jorbunden," "Frem," March 19th, 1899.) 



The probable reason that the great majority of the 

 volcanoes of the earth are grouped along the western 

 borders of the Pacific and around the Gulf of Mexico, is 

 primarily that these regions are, or have until recently, 

 been areas of great sedimentation. The longest rivers flow 

 into these parts, but the most potent factor, perhaps, in 

 bringing about this heavy sedimentation is the profuse 

 organic growth, consisting of corals, nullipores, Lithotham- 

 nion and Halimeda, of polyzoa and foraminifera, and marine 

 mollusca. The Equatorial currents in both the Atlantic 

 aud the Pacific, flowing from east to west, ensure that the 

 waters in the western portions of these basins are several 

 degrees warmer than in the eastern parts. 1 Everything is 

 favourable to the sustenance of life. The heavy sedimen- 

 tation going on induces subsidence, thus gradually accentu- 

 ating in these parts the folds that mark the oceanic borders. 

 It must not be understood that I look upon sedimentation 

 and erosion as the main causes of inequalities of the earth's 

 surface. This fallacy has been ably exploded by Huttoii. 2 



1 " Allegemeine Erdkunde/' Vol. i., pp. 2938, 294, and fig. 84, by Hr. 

 J. Haun. 



2 Presidential Address in Section C. — A.A.A.S., Vol. n., 1890, Melbourne 

 Session—" Oscillations of the Earth's Surface." 



