434. TRANSACTIONS OF SECTION A. 
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 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 combined effect represented 
by the zonal harmonic and the tesseral harmonic of rank 1 is a furrowed 
surface with an Arctic region of depression extending southwards in the direc- 
tion of the Atlantic, a zone of elevation which runs across the Atlantic, South 
America, and Africa, and then turns northwards at either end, a zone of de- 
pression with the same kind of contour, and an Antarctic region of elevation 
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which extends northwards in the direction of Australasia. These regions are 
shown in fig. 10. J have recorded the result of combining these two harmonics 
because they represent the particular effects that would be produced by the inter- 
action of two causes—the rotation, and the eccentric position of the centre 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 means of the equator 
and two complete meridian circles. Alternate octants are elevated and depressed 
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as shown in fig. 11. Wecan name the octants where there is elevation: Asia, 
Australasia, North America, 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 division of the surface into six 
sectors by means of three complete meridian circles. Alternate sectors are 
depressed and elevated as shown in fig. 12. The southward tapering of Africa is 
specially associated with the harmonic of this type. The combined effect of all 
the harmonics of the third degree is shown in fig. 13. It represents the sphere 
deformed into a sort of irregular pear-shaped surface. The stalk of the pear is in 
the southern part of Australia and contains Australasia and the Antarctic continent. 
