II 



THE FIGUEE OF THE EARTH 



history of discovery into the form of the earth, 

 -L beginning with the three famous voyages of 

 Columbus, Vasco de Garna, and Magellan, and even 

 yet not brought to an end, constitutes one of the most 

 interesting chapters in the story of our science. Soon 

 after the demonstration of its generally spherical form, 

 Newton showed, as a deduction from mechanical prin- 

 ciples, that its true figure should depart from that of a 

 sphere in the direction of an oblate spheroid, and he was 

 able to calculate from first principles what the difference 

 in length of its polar and equatorial diameters should be. 

 As we now know, the result he obtained was surprisingly 

 near the truth. In popular language, the earth, accord- 

 ing to Newton, was shaped like an orange. Later the 

 French astronomers, led by Cassini, concluded, and quite 

 justly, that, judged from the measurements then existing 

 of arcs of meridians in different localities, the form of the 

 earth could not be that of an orange, that the polar 

 diameter, instead of being shorter than the equatorial, 

 as Newton supposed, was in fact longer, and that thus 

 the true form was more like that of a lemon. Hence 

 arose the controversy, celebrated by Swift in "Laputa" 

 as the battle between the " little-endians " and the " big- 



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