394 DYNAMICAL GEOLOGY. 



(1) The gathering of the dry land, the continents, the earth's individ- 

 ualities, and arenas of progress, mostly toward the north pole, and of the 

 waters as largely toward the south pole, the great cause of continental differ- 

 ences in the system of progress. 



(2) The attitude of the continents on the globe, each mass having the 

 broader extremity to the north and narrowing southward — a fact which 

 Bacon, in his Novum Organum, set forth as a problem for solution. 



(3) The zigzag arrangement of the northern and southern continents. 

 South America having its center 40° east of that of North America, and 

 Australia, as far east of that of Asia. 



(4) The separation of the northern and southern continents by a volcanic 

 belt that girts the sphere. 



(5) The two systems of courses in the grand feature-lines of the conti- 

 nents and oceans nearly at right angles with one another, the more equatorial 

 and most prevalent varying between IST. 60° W. and IST. 70° W., but curving 

 to N. 30° W., and the transverse system with correlate variations. 



(6) The existence of a greater mean depth in the western half of the 

 Atlantic and Pacific Oceans than in the eastern half, notwithstanding 

 the fact that the continental border adjoining the west Pacific is a region of 

 high mountains with many volcanoes in the continental islands, and that 

 the border adjoining the west Atlantic has the lower mountains of North 

 America and no volcanoes. 



These characteristics of the earth necessarily date from the beginning of 

 solidification ; and the first — the existence of a larger part of the continental 

 masses in the northern hemisphere and of the oceanic area in the southern — 

 may have involved the others. For, if the alleged excess of density in the crust 

 beneath the oceans is owing to the prevalence of basaltic rocks, the crust of 

 the oceanic basin would have remained in fusion after that of the continental 

 had generally cooled through an era long enough for a loss of 300° to 500° 

 Fahrenheit, — a fact that would have determined differential conditions and 

 consequences at the first cooling of the earth's crust. 



The zigzag arrangement of the continents has been attributed to torsion ; 

 and the belt of volcanoes that girts the world has been pointed out as the 

 belt of maximum torsion, and the courses of the earth's feature-lines as 

 consequences in part of the pressure or tension attending torsion ; and thus 

 an explanation that reaches deeply into the subject of origins has already 

 been presented. 



W. L. Green (1875 and 1877), in The Vestiges of a Molten Globe, sug- 

 gested the idea that the mass of the continental plateaus, occupying the 

 northern hemisphere, caused, during the incipient stage of the first formed 

 crust, a retardation in the rotation of this part of the floating crust, and 

 thereby "a shearing strain . . . between the crusts of the northern and 

 southern hemispheres," and hence a yielding to this strain along the earth's 

 great volcanic belt ; remarking that thus " South America became separated 

 from its northern half continent, and pushed toward Africa," while Asia, in 



