776 GEOGRAPHICAL LATITUDE. 



determiue the length of a degree, and therefrom, by farther deductions, 

 the size and form of the earth. The principal aim of this great work 

 was, to be sure, purely scientific ; but that it has a most practical appli- 

 cation also is pithily stated byMaupertuis as follows: "Sur des routes 

 de 100 degres, en longitude, on commettroit des erreurs de plus de 2 

 degres, si uaviguant sur la spheroide de Newton on se croyoit sur 

 celui du livre De la grandeur et figure de la terre: and combien de 

 vaisseaux ont peri pour des erreurs moins considerables.' -For ages 

 those who believed in the rotundity of the earth thought it to be a 

 perfect sphere; but in the seventeenth century the two great physicists 

 of the day, Newton and Huygheus, again starting with different hyi)oth- 

 eses, came to a like result, viz, that the earth is not a true sphere, but 

 rather a spheroid, flattened toward the poles. The announcement of 

 these theories, nearly at the same time (1686 and 1688, respectively), 

 caused great excitement among the astronomers and geographers; two 

 camps were formed contending respectively for the old and the new 

 theory and each demanding proof of its theory by surveying: for if 

 the earth is flatter toward the poles, a degree of latitude will be longer 

 near the pole than near the equator. France, which was already the 

 leading country in such work, offered a good field for it; the French 

 astronomers were eager to undertake it, and Louis xiv authorized the 

 surv^ey of a meridian extending throughout the land. The northern 

 and southern stretches being put under leading specialists for survey, 

 the result showed the degree to be longest in the southern section ; a 

 repetition only confirmed the result. If the surveys were correct, this 

 proved the earth to be elongated toward the poles, instead of flattened. 

 Great was the delight of the French at this defeat of the foreign 

 theorists. But the latter contended that the matter was by no means 

 settled ; that the only sure method would be to make surveys near the 

 equator and near the pole, and await the result. This plan was carried 

 out during the first half of the eighteenth century, and resulted in the 

 complete triumph of the defenders of the theory of flattening toward 

 the poles. This point settled, the earth was still sup[)osed to be a per- 

 fectly symmetrical figure ; but as surveys became more extensive and 

 more accurate there appeared inequalities which were not compatible 

 with that theory, and it is now generally accepted that beyond the 

 irregularities of mountains and valleys, discernible to every eye, the geo- 

 detic form of the earth is also irregular. 



We have already seen that astronomy gives us the means of deter- 

 mining accurately and with comparative ease the latitude of any one 

 place. If then the latitude of two places which are on the same merid- 

 ian is known and the distance between them is accurately measured, 

 supposing the earth to be a perfect sphere, a simple arithmetical cal- 

 culation \f\\\ give the earth's circumference; for the latitude being 

 expressed in degrees, of which 360 form the circumference, the distance 



' Maupertuis, (Euvres, iii, 8I<J. 



