late D'lfcov cries In Science. 129 



the following proportion: 1° i' 13" is to 58233 toifes as 

 1° o' o" is to a fourth term, found to be 57074 toifes. This 

 is the length of a degree of the earth between Paris and 

 Amiens, determined by Picard. The mean latitude of this 

 degree is 49° 23'. This length fuppofes the toife of the 

 north, and the temperature of Reaumur's thermometer, 10 

 or 12". This degree is reduced to 57056 with the toife of the 

 equator now adopted." 



It is to be obferved, that according to ihefe new meafure? 

 the difference of the degree between Evaux and Carcaflbnne 

 is much greater than it ought to be according to theory ; for 

 it differs 88 toifes from that betyveen Paris and Evaux, thought 

 there is only a difference of about three degrees of latitudCj 

 which makes nearlv 32 toifes per degree. That between 

 CarcafTonne and Mountjouy differs 34 toifes, though there 

 is only a difference of about two degrees of latitude, which, 

 makes 14 toifes per degree 3 while the degrees between t)un* 

 kirk and Paris differ but 10 toifes, and there are two degrees 

 of latitude, which makes only four toifes of difference pet 

 degree. 



It is generally fuppofed that the degree under the equator 

 is 56753 toifes, as it has been eftimated by the French aca- 

 demicians, and that under the p«lar circle, it is 57419 toifes, 

 which would make a mean difference of about feven toifes 

 between each degree. But it appears that the difference is a 

 little o:reater between the degrees towards the pole, than be- 

 tween thofe towards the equator. The difference of 14 alid 

 32 toifes, which has been lately found, cannot be reconciled 

 with general theory. This difference, therefore, muff depend 

 on fome particular caufes, Thefe fa6ts indicate either an 

 irregularity in the terrcftrial meridians, or an cllipticity in 

 the equator and its parallels, or an irregularity in the inte- 

 rior of the earth, or an effe6t of the atlraftion of mountains, 

 or a powerful aftion of thefe different caufes united, or of 

 fouie of them on each other; an a61;ion which lias nevef 

 been dcmonftratcd in fo ftriking a manner as by the refults* 

 juft given. It muff; be left to the ablcft mathematicians to 

 diredt their attention to thefe fadts in order that they may 

 endeavour to explain the principlca on which they depend, 



Vol. VI. S and 



