[ 357 3 
Tember 2. 1749. I am ftill thoroughly convinced 
of the Truth of what I advanced therein, that the 
Orbs of the Planets continue to be contra&ed, and 
confequently their periodical Times grow fhorter. 
But in order to put this Faft out of Doubt, we 
ought to be furnifhed with good ancient Obferva- 
tions, and alfo to be very Hire of the Time elapfed, 
fince thofe Obfervations, to this Day: Which we 
aft nor, with regard to the Obfervations that Ptolemy 
has left us. For Chronologifts, in fixing the Mo- 
ments of thofe Obfervations, run into a Miftake, 
by fuppofing the Sun’s mean Motion to be known; 
which ought rather itfelf to be determined by thefc 
fame Obfervations. Now, if we reduce the Days 
marked by Ptolemy to the Julian Kalendar, we run 
the Rifque of committing an Error of a Day or 
two, in the whole Number of Days elapfed, from 
that to our Time ; becaufe the Courfe of the 'Julian 
Years, according to . which every fourth ought to 
have been Biffextile, has been frequently interrupted 
by the Pontifices ; cf which we find fome fine 
Marks in Cenforinus and 'Dion CaJJius. Wherefore 
it might well happen, fince the Times mark’d by 
Ptolemy , that there has really been a Day or two 
more than we reckon, and confequently, that 
Ptolemy' s Equinoxes, ought to be put a Day or tw T o 
back; which would lengthen the Years of thofe 
Times. I was in hopes, that the Arabian Obferva- 
rions would .not be liable to this Inconvenience 
bccaufc the Julian, Kalendar has not been interrupted 
for thefe lalt paft twelve hundred Years. The late 
Dr. Halley had alfo remark’d, that the Revolutions 
of the Moon are quicker at prefent than they were 
Z z in 
