536 



SCIENCE 



[N. S. Vol. XXVI. No. 669 



The existence of an Antarctic continent and 

 an Arctic Ocean is specially associated with 

 the presence of this harmonic, and the dis- 

 proportion of the continental areas in the 

 northern and southern hemispheres is also 

 connected with it. The second of the 

 harmonics of the third degree, the tesseral 

 harmonic of rank 1, gives us a division of 

 the surface into six half -zones by means of 



Fig.9. 



a complete meridian circle and the parallels 

 of latitude about 27° north and 27° south. 

 Alternate half -zones are depressed and 

 elevated as shown in Fig. 9. The com- 

 bined effect represented by the zonal har- 

 monic and the tesseral harmonic of rank 

 1 is a furrowed surface with an Arctic 

 region of depression extending southwards 

 in the direction of the Atlantic, a zone of 

 elevation which runs across the Atlantic, 

 South America and Africa, and then turns 



Fig.lO. 



northwards at either end, a zone of de- 

 pression with the same kind of contour, 

 and an Antarctic region of elevation which 

 extends northwards in the direction of 

 Australasia. These regions are shown in 



Fig. 10. I have recorded the result of 

 combining these two harmonies because 

 they represent the particular effects that 

 would be produced by the interaction of 

 two causes— the rotation, and the eccentric 

 position of the center of gravity. The 

 third type of harmonics of the third degree, 

 the tesseral harmonic of rank 2, gives us 

 a division of the surface into octants by 



Fig. II. 



means of the equator and two complete 

 meridian circles. Alternate octants are ele- 

 vated and depressed as shown in Fig. 11. 

 We can name the octants where there is 

 elevation: Asia, Australasia, North Amer- 

 ica, South America. The harmonic of this 

 type is certainly prominent. It is specially 

 associated with the skew position of South 

 America to the east of North America. 

 The fourth type of harmonics of the third 

 degree, the sectorial harmonic, gives us a 



Fig, 12. 



division of the surface into six sectors by 

 means of three complete meridian circles. 

 Alternate sectors are depressed and ele- 

 vated as shown in Fig. 12. The southward 

 tapering of Africa is specially associated 



