420 Mr. Marsden on the Era of 
dered in what order and method thefe additional or intercalary 
days Ihould be inferted, fo as to «ife£ the compenfation re- 
quired with as much equability as poflible, anch maintain a 
correfpondence, as near as circumftances would admit, with 
the periods marked by the phafes of the moon. The follow- 
ing are the years to which, for reafons that fhall be' afterwards 
affigned, it was judged proper to annex an extraordinary day, 
and which (in contradiftindlion to thofe 19 that have only 354 
days) are termed years of excefs, viz. the 2d, 5th, 7th, 10th, 
13th, 1 6th, 18th, 2 iff, 24th, 26th, and 29th, of the cycle of 
thirty years. 
Their months, conformably with thofe of the Hebrew ca- 
lendar, it was determined fhould confift alternately of 30 and 
29 days; and therefore, in an ordinary or fimple year of 354 
days, the twelfth and laft month, Dulhajee, would have only 
29 ; but, in the years of excefs, the intercalary day is added to 
this month, which is then made to confift of 30 days, and the 
year, confequently, of 355 days (w). Thus, for example, 
in the year of Chrift 622, the Hejera commenced on the 16th 
of July, with the Arabian month 
Moharram, 
which had 
Days. 
3 ° 
Safar 
• m 
29 
Rabee prior 
- 
30 
Days. 
Moharram,inthe 2d year, had 
Safar - 
Rabee prior 
2 9 
3 ° 
Carried over 89 
Carried over 
falls fhort of thirty complete lunar years, by fomething more than 17, and con- 
fequently advances one day in about 2500 years. The Chaldeans, who made 
the time of the revolution to confift of onefcruple, or 1080th part of an hour, 
more than the Arabs thought fit to allow, were wonderfully near to the truth (/). 
If, inftead of thirty years, a cycle of nineteen had been chofen, and feven 
days intercalated, there would have been an excefs of a thirtieth part of a day, 
which would have caufed the reckoning to retrograde one day in 570 years. 
Rabee 
