VOL. LXXX.] PHILOSOPHICAL TRANSACTIONS. 751 



tinguished by a liberal policy; and the gentlemen above alluded to attribute to 

 them respectively, not the interdiction but the restitution of the solar reckoning ; 

 that of the Mahometans, imposed on the province by their more bigotted pre- 

 decessors, being found inconsistent with the periodical collection of the revenue, 

 which depends on the harvests. It is, in truth, extremely difficult to conceive 

 how a mode of computation, so much at variance with the rational concerns of 

 civilized people, can possibly subsist in any state of society above that of the 

 pastoral and predatory tribes with whom it originated. 



As it appears, that the people of Siam, in the farther India, have borrowed 

 their knowledge of astronomy from the Hindoos, it will not be thought incon- 

 sistent with the present subject, to add some account of the chronological eras in 

 use among them. Of these, one has been termed their civil, and another their 

 astronomical era. The civil reckoning is by lunar years, consisting of 12 months 

 each, with an intercalation of ^ months in the period of 19 years, and commenc- 

 ing with the new moon that precedes the winter solstice. This era is computed 

 from the supposed time of the introduction of their religion by Sommona-codom, 

 544 years before Christ, or in the year of the Julian period 4169 ; and conse- 

 quently 2333 years of it were expired in the month of December 1789 ; but by a 

 custom which, though not without its parallel, wants to be satisfactorily explained, 

 they do not change the date, or count the succeeding year 2334, till it meets the 

 astronomical reckoning in the month of April following. 



The astronomical era is founded immediately on the tables and modes of calcu- 

 lation adopted from the Hindoos. The French astronomer, Dom. Cassini, by an 

 ingenious deduction from no very circumstantial data, inferred that it must have 

 had for its epoch a mean conjunction of the sun and moon, which happened on 

 March 21, 638 of the Christian era. This preceded by a few hours the com- 

 mencement of the established Hindoo year, to which it was evidently meant to be 

 accommodated, though it is by him referred to the vernal equinox, which took 

 place 2 days earlier. The length of the Siamese solar year he found to be 6Qb^ 

 gh 22,m 36s^ and consequently 1152 years of the era should expire on the llth 

 April 1790, when the sun enters the Indian zodiac, being 5 60 years later than 

 the era of Salaban. For want of corroborating facts, this determination of an 

 epoch by M. Cassini vVas considered as speculative and uncertain ; but Mr. M. 

 was in possession of a date which, though not precise, may serve generally to 

 authenticate it. " In 17 69, the king of Pegu (a country bordering on Siam, 

 and formerly conquered by it) dates his letter to the French at Pondicherry, the 

 12th of the month Kchong J 132." This makes 1790 to correspond with 1153 

 instead of 1152; but when we consider the vague manner in which notices of 

 this kind are given, a difference of 1 year can scarcely be urged as an objection. 



The Siamese were also accustomed to make use of a cycle of 60 years, ex- 



