length of its circumference, being used in India before it was known in Europe*.

The existence of the Indian astronomy was not known in Europe till M. de la Loubere, ambassador of Louis XIV. at the court of Siam, brought with him to France some tables and rules for calculating the places of the sun and moon, which were examined by Cassini, who bore testimony to their accuracy. Other tables were sent to Paris by the French missionaries; and M. le Gentil, on his return from India, where he had been to observe the transit of Venus, A. D. 1769, brought with him another set of tables, and the Indian methods of calculating; and in 1787, M. Bailly published his Astronomie Indienne, while in 1789 Mr. Playfair's paper on the same subject appeared in the Edinburgh Transactions. Such was the state of knowledge on this highly interesting subject when the Asiatic Society was established. Since that time, the volumes of their Researches have been enriched with a variety of papers on the Indian astronomy, from which I take the facts I write to you, in hopes that though I understand nothing whatever of the science myself, you may be induced, in the East, to go

* See Mr. Davis's paper, in the second volume of the Asiatic Researches.

on with studies in which I know you have already made some progress.

The Hindû books on astronomy have the general name of the Jyotish Sastras, in which are to be discovered traits of a bright light, which must have illumined mankind at so very early a period, that M. Bailly seems to doubt whether we should not regard them as remains of antediluvian science, fragments of a system that is lost, and whose ruins only serve to excite our admiration.

The Surya Sidd'hanta* seems to be the Jyotish Sastra of highest authority, if it be not the oldest. It is said to have been revealed by Surya, or the sun, to the sage Meya, according to some about the year of the world 1956. The obliquity of the ecliptic is stated in it to be 24°, which, if founded on actual observation at the time of compiling that Sastra, would confirm its supposed antiquity.

The Hindû division of the zodiac into signs

* Abul Fazzle, in the Ayeen Akberi, enumerates nine siddhantas or treatises on astronomy: 1st, the Brahma Sidd❜hanta; 2d, Surya Sidd'hanta; 3d, Soma Sidd'hanta; 4th, Vrihaspati Siddhanta; 5th, Goorg Sidd'hanta; 6th, Nareda Sidd'hanta; 7th, Parasara Sidd'hanta; 8th, Poolustya Sidd' hanta; 9th, Vashishtha Sidd'hanta. But there are many other treatises on the subject, either original works or commentaries on the ancient books.

is

and degrees, is the same as ours. Their year sidereal, and commences at the instant of the sun's entering the sign Aries, each astronomical month containing as many days and fractions of days as he stays in each sign. The civil time differs from the astronomical year, in rejecting the fractional parts, and the civil year and month are begun at sunrise instead of midnight.

The epocha from which the Hindûs compute the motions of the planets, is that point of time counted back, when, according to their motions, they must have been in conjunction at the first point of Aries, or above a thousand millions of years ago, it will take nearly double that period before they are again in the same situation; and the enormous interval between these conjunctions is called a calpa, and mythologically a day of Brahma. The calpa is divided into manuantaras, and great and little yugs, the use of some of which divisions is not now apparent; but the greater yug is an anomalistic period of the sun and moon, at the end of which they are found together in the first of Aries. The division of the great yug into the Satya, Treta, Dwapar, and Cali yugs, are by some supposed to have originated in the precession of the equinoxes (Cranti), but by others they are considered as purely mythological, like the golden,

silver, brazen, and iron ages, among the western poets.

The really learned Jyotish Pandits have just notions of the figure of the earth, and of the œconomy of the universe; but they, in appearance, agree with the popular notions on these subjects such as, that eclipses are caused by a monster who occasionally interposes his head or his tail (Cetu and Rahu, or the ascending and descending nodes) between the earth and the sun and moon; and that the earth is a plain, supported on the backs of elephants, resting on a tortoise, and other equally puerile superstitions.

But to return to the Jyotish Brahmins: one of their methods for finding the latitude is by an observation of the Palabha, or shadow projected from a perpendicular gnomon, when the sun is in the equator; and the longitude is directed to be found by observation of lunar eclipses, calculated for the first meridian, which the Surya Siddhanta makes pass over Lanca Rohitaca, Avanti (now Ougein) and Sannihita

saras.

In the Surya Sidd'hanta, the method of observing the places of the stars is briefly hinted, "The astronomer should frame a sphere, and examine the apparent latitude and longitude." Commentators on this passage describe the method of making the observation. They direct a sphe

rical instrument (golayantra*) to be constructed. On the pins of the axis of the sphere must be suspended an intersecting graduated circle, which appears to be a circle of declination. The golayantra is then rectified, so that the axis points to the pole, and the horizon is true by a water level. "The instrument being thus

This is an armillary sphere. Various directions for constructing it occur in different astronomical books of the Hindûs, among others in the Sidd'hanta Siromani, by Bhascara an astronomer, who flourished in the twelfth century of the Christian æra. But there is one contained in the Surya Sidd❜hanta as follows, in a literal translation.

"Let the astronomer frame the surprising structure of the terrestrial and celestial spheres.

"Having caused a wooden globe to be made (of such size) as he pleases, to represent the earth; with a staff for the axis, passing through the centre, and exceeding the globe at both ends; let him place the supporting hoops as also the equinoctial circle.

I

"Three circles must be prepared (divided for signs and degrees) the radius of which must agree with the- respective diurnal circles, in proportion to the equinoctial: the three circles should be placed for the ram and following signs, respectively, at the proper declination in degrees north or south; the same answer contrariwise for the Crab and other signs. In like manner three circles are placed in the southern hemisphere for the Balance and the rest, and contrariwise for Capricorn and the remaining signs. Circles are similarly placed on both hoops, for the asterisms in both hemispheres, as also for Abhijit, and for the seven Rishis, Agastya, Brahme, and other stars.