the Mahometans , called the Hejerct . 4 1 9 
purpofe*. Particular attention is due to the explanation of this 
mode, both as being more artificial and complex, and becaufe 
it ferves to regulate the dates in matters of hidorical record, 
and indeed of all writings where pretenfion is made to accu-- 
racy (Jt). Upon this the Turkifh, Moorifh, and every fyde- 
matic Mahometan calendar are founded. 
The lunar month, or mean fynodic revolution, according 
to the computation of the Arabian adronomers, confids of 29 
.days, 12 hours, and 792 fcruples or parts in 1080; and tiie 
year of 354 days, 8 hours, and 864 fcruples. But, as the 
purpofes of mankind require that the year fhould contain an 
integral number of days, it became expedient to collect and 
difpofe of thefe fradtional exceedings in a confident and prac- 
ticable manner ; and with this view, a cycle or period of 
thirty lunar years was chofen, as the lowed number that ad- 
mitted of their being formed into days, without fenfible defi- 
ciency or remainder. Their fum being 1 1 days, it was deter- 
mined that 1 9 of thofe thirty years fhould be compofed of 
354 days, and 11 of 3^5 days each. The judnefs of this 
proportion will equally appear, if it be obferved, that 8 hours 
and 864 fcruples (or 48 minutes) conditute 11 parts in 30 of 
twenty-four hours, and confequently in thirty years produce 
an excefs of 1 1 whole days f. It remained next to be confi- 
dered 
* A paflage in Alfraganus (who wrote about the year of Chrift 950) would 
lead us to infer, that, befide the two ways of computing time here diftinguilhed, 
the Aftronomers were accuftomed to follow a third, whofe periods were marked 
by the conjunction of the luminaries : but, as this learned Mahometan was a 
profefled ftudent of Ptolemy’s works (which in this place he quotes), we may 
conclude, that, when he fpeaks of aftronomers, he does not mean to confine the 
expreftion to thoie of his own country or religion (/'). 
f The mean fynodic revolution being 29 d. 1 % h. 44' and nearly 3", this cycle 
Vol. LXXVIII. Kkk falls 
