predicted by Thales. 237 
I have before observed, that all these calculations have been 
made from the Tables Astrojiomiques, lately published in France: 
which tables have since been adapted to the meridian of Green- 
wich, and to astronomical time, by Mr. Vince, and inserted 
by him in the third volume of his System of Astronomy.* In 
these tables are given the secular variations in the moon's mean 
longitude, mean anomaly, and mean distance from her node, 
as deduced from the formulae of M. Laplace. It is with much 
deference that 1 presume to question the accuracy of the re- 
sults, obtained by means of those formulae ; but, as the present 
subject is in a great measure connected with that inquiry, I 
shall briefly state my reasons for offering a doubt upon that 
point. 
It is well known that Agathocles, king of Syracuse (when 
besieged in that city by Hamilcar, the Carthaginian general), 
undertook the bold design of invading Africa, and thereby 
moving the seat of war from Sicily. He accordingly embarked 
a numerous army, and set sail for the continent. The day 
after he left Syracuse, the fleet was terrified at an eclipse of 
the sun ; which was so great, that, in the words of Diodorus 
# It is to be regretted, that Mr. Vince did not adapt his tables to the English 
system of chronology likewise. For the years before Christ, according to the English 
mode of computation, exceed by unity the corresponding years given by the French 
chronologists : since they make the year of Christ equal to o, whereas the English 
reckon it as i B. C. — The French also assume the year 1582 as the date of the Re- 
formation of the Calendar ; whereas, in England, that event did not take place till 
the year 1752. 
Without a proper attention to these circumstances, we may be led into an error of 
one v/hole year, in the calculation of the places of the heavenly bodies for any period 
prior to the Christian era; and into an error of ten or eleven days in our calculations 
for that space of time which is included between October 5th, 3582, and September 
14th, 1752. 
