the Weight of Continents and Mountains. 267 



it will therefore, I think, be proper to adhere to the 1500 

 meters for the greatest height and depression. 



We have next to consider what order of harmonic inequali- 

 ties is most nearly analogous to the great terrestrial continents 

 and oceans. The most obvious case to take is that of the two 

 Americas and Africa with Europe. The average longitude of 

 the Americas is between 60° and 80° W., and the average lon- 

 gitude of Africa is about 25° E., hence there is a difference of 

 longitude of about a right-angle between the two masses. 

 These two great continents would be more nearly represented 

 by an harmonic of the sectorial class/- rather than by a zonal 

 harmonic, nevertheless I think the solution for the zonal har- 

 monic will be adequate for the present purpose. 



Now it has been explained above that the harmonic of the 

 fourth order represents an equatorial continent and a pair of 

 polar continents. In the case of the fourth harmonic therefore 

 there is a right angle of a great circle between contiguous con- 

 tinents. We may conclude from this that the large terrestrial 

 s are about equivalent to the harmonic of the fourth 

 order. 



Table V {b), § 7, gives the maximum stress-differences 

 under the center of the equatorial elevation of the several 

 zonal harmonics, the height of each being 1500 meters, f The 

 point at which tins maximum is reached is given in each case, 

 ;i| i'l Plate xx, li--. 4, illustrate* L'Mipim- illy the law of variation 

 of stress- difference. 



The second harmonic cannot be said to represent a conti- 

 nent, and the table shows that in each of the other cases the 

 maximum stress clin'erciice is very nearly four tons per square 

 inch. The depths of the maximum point are of course very 

 different in each case. 







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