Chap. 14] . ACCOUNT OF THE WOELD. 47 
of the others is more difficult, and has never been laid down 
by any one before me\ 
CHAP. 14. (17.) — WKY THE SAME STAES HATE DIEFEEEFT 
MOTIONS. 
I must first state the cause, why the star Venus 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 degrees respectively ? They in reality 
do so, but the theory fails us here. Eor 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, ii. 
276. 
2 According to Ptolemy, these numbers are respectively 47° 51' and 
24° 3' ; the modern astronomers have ascertained them to be 48° and 29°. 
The least elongations of the planets are, according to Ptolemy, 44° 7' and 
18° 50', and according to the observations of the moderns, 45° and 16° 5 
Marcus in Ajasson, ii. 354. 
3 I have not translated the clause, " quum sint diversse stellse," 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 Yalpy and Lemaire, but is retained by Poinsinet and 
Ajasson. 
,. 4 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 SoKs distantiam pervenerunt, ultra procedere non 
possunt, deficiente circuh longitudine, id est, ampHtudine." Alexandre in 
Lemaire, ii. 277. 
^ The transits of the inferior planets had not been observed by the 
ancients. 
