Chap. 14.] ACCOUNT OP THE WOELD. 47 



of the others is more difficult, and has never been laid down 

 by any one before me^ 



CHAP. 14. (17.) — WHY THE SAME STAE8 HATE DIFFEBEITP 

 MOTIONS. 



I must first state the cause, why the star Yenus never 

 recedes from the sun more than 46 degrees, nor Mercury more 

 than 23'', while they frequently return to the sun within this 

 distance'. As they are situated below the sun, they have 

 both of them their apsides turned in the contrary direction ; 

 their orbits are as much below the earth as those of the 

 stars above mentioned are above it, and therefore they cannot 

 recede any farther, since the curve of their apsides has no 

 greater longitude\ The extreme parts of their apsides 

 therefore assign the limits to each of them in the same 

 manner, and compensate, as it were, for the small extent of 

 their longitudes, by the great divergence of their latitudes*. 

 It may be asked, why do they not always proceed as far as 

 the 46th and the 23rd de^es respectively ? They in reality 

 do so, but the theory fails us here. Por it would appear 

 that the apsides are themselves moved, as they never pass 

 over the sun''. "When therefore they have arrived at the 



^ Alexandre supposes, as I conceive justly, that our author, in this 

 passage, only refers to the writings of his own countrymen ; Lemaire, iL. 

 276. • 



2 According to Ptolemy, these numbers are respectively 47° 51' and 

 24° 3' ; the modem astronomers have ascertained them to be 48° and 29**. 

 The least elongations of the planets are, according to Ptolemy, 44° 7' and 

 18° 60', and according to the observations of the modems, 45° and 16° j 

 Marcus in Ajasson, ii. 354. 



* I have not translated the clause, " quum sint diversse stella," as, 

 according to Hardouin, it is not found " in probatissimis codd,," and 

 appears to have httle connexion with the other parts of the sentence ; 

 it is omitted by Valpy and Lemaire, but is retained by Poinsinet and 

 Ajasson. 



* When these inferior planets have arrived at a certain apparent 

 distance from the sun, they are come to the extent of their orbits, as seen 

 from the earth. 



^ " Quum ad illam Solis distantiam pervenerunt, ultra procedere non 

 possunt, deficiente circuli longitudine, id est, ampUtudine." Alexandre iu 

 Lemaire, ii. 277. 



® The transits of the inferior planets had not been observed by the 

 ■ancients. 



