of the Earth by means ofOccultalions of the fixed Stars. 357 



with the great differences, above mentioned, in the duration of 

 occultations. 



§ 14. The different meastirejnents of the degrees of the meri' 

 dian are hkevvise so discordant amongst themselves, that the re- 

 spectable author (whom I am about to quote) asserts that the 

 greater the number of degrees that are measured, the more uncer- 

 tain does the figure of the earth seem to be*. Let us moreover 



bear 



* This indeed appears to be the case from some of the late measurements. 

 With respect to the meridian of France, M. Delambre states {Traite cC Astro- 

 nomie, vol. iii. page 567) that " it was hoped that the measurement of that 

 arc (divided nearly into two equal parts by the parallel of Evaux) would have 

 given the quantity of the compression of the earth's axis. The calculation, 

 however, makes it = -r^\ a quantity mi;ch too great. The whole arc, com- 

 pared with that of Bouguer at Peru, makes it = j-J-^ ; which is too small." 

 And he goes on to observe that, from a revision of the calculations of Lacon- 

 damine, and taking a mean between him and Bouguer, he lias deduced the 

 quantity -^J^ ; which he considers as the most probable one, and which he 

 proposes to be adopted in all future calculations. Nevertheless he afterwards 

 states {Ibkl. page 572) that a " compression of -r^j^ represents very well the 

 arcs between Greenwich and Paris, between Dunkirk and Paris, between 

 Greenwich and Evau.x, between Greenwich and Barcelona, and between Car- 

 cassonne and Mount-Jouy. It appears then (he adds) that, without much 

 variation, t!;e arc of the meridian from Greenwich to Barcelona, indicates 

 (in the whole and in its several parts) a compression which diifers very little 

 from T-io' ' -A-fd the conclusion, which he draws from the whole, is that 

 " the arc of France indicates a compression more considerable than that of 

 the globe in general." It is worthy of observation that Maupertuis, who was 

 one of the astronomers that measured the arc of the meridian in Sweden in 

 1736, makes the compression = T-fTT> ^^ ciriparing it with the arc then 

 measured in France. But, M. Svanberg who, in 1805, remeasuredthe same 

 arc, deduces the compression = ■575VT when compared ^dth the arc recently 

 measured in France ; and = ^^Vr ""hen compared with that of Bouguer 

 at Peru. This is however on the presumption that the standard measure, 

 used in the survey, was equal to the double metre at zero of the thermo- 

 meter : but, if it was so only at the temperature of + 16"|, the corresponding 



...ipressions would be ;5^|;.-g, and ;y^V'T- Other results are obtained ac- 

 ■iJing to the different tables of refraction made use of in the calculations; 

 iO that, after ail, considerable doubts exist as to the exact quantity of the 

 compreision, as deduced from that survey. M. Delambre, from the mea- 

 surements, given by Major Lambton, of an arc in the East Indies, stated the 

 compression = ■jj5'j.Y • ''"t> from the subsequent operations of the same 

 gentleman, heafteruards deduces it = ^^^. Major Lambton himself, how- 

 ever, from a more recent measurement has stated tb.e compression to be = 

 "uiii' ''"ti that on comparing the whole of his arc with the whole of the 

 French arc, the compression would be = ■^;^. A remarkable discordance 

 in the results. The measurement of Lacaille, at the Cape of (iood Hope, 

 compared with tiiat at the equator, gives x-]iS- J^astly, ' shall add that the 

 recent measurement of the arc, in England, seems to indicate a /fro/oji^'w^io/i, 

 instead of a coiuprasshm of the polar axis. Tliesc discordant conclusions 

 leave a very unsatisfactory imj)ression on the mind, notwithstanding the ac- 

 Z 3 knowlcdged 



