Excerpts from Dharampalji's book Indian Science and Technology in the 18th Century (1971)
instrument exhibited a mathematical exactness in the fixing, bearing, and fitting of the several parts, in the necessary and sufficient support to the very large stones that composed them and in the joining and fastening each into the other by means of lead and iron.
The situation of the two large quadrants of the instrument marked A in Fig.1 whose radius is nine feet two inches, by there being yet right angles with a gnomon at twenty five degrees elevation, are grown into such an oblique situation as to render them the most difficult, not only to construct of such a magnitude, but to secure in their position for so long a period, and afford a striking instance of the ability of the architect in their construction; for, by the shadow of the gnomon thrown on the quadrants, they do not appear to have altered in the least from their original position; and so true is the line of the gnomon, that, by applying the eye to a small iron ring of half-an-inch diameter at one end, the sight is carried through three others of the same dimension to the extremity at the other end, distant thirty-eight feet, eight inches, without obstruction; such is the firmness and art with which this instrument has been executed. This performance is the more wonderful and extraordinary when compared with the works of the artificers of Hindustan at this day, who are not under the immediate direction of an European mechanic; but arts appear to have declined equally with science in the east.
Lieutenant-colonel Archibald Campbell, at that time chief engineer in the East India Company's service at Bengal, a gentleman whose abilities do honour to his profession, made a perspective drawing of the whole of apparatus that could be brought within his eye at one view; but I lament he could not represent some very large quadrants, whose radii were about twenty feet, they being on the side from whence he took this drawing. Their descriptions however is, that they are exact quarters of circles of different radii, the largest of which I judged to be twenty feet, constructed very exactly on the sides of stone walls
built perpendicular, and situated, I suppose, in the meridian of the place: a brass pin is fixed at the centre or angle of the quadrant, from whence, the Bramin informed me, they stretched a wire to the circumference when an observation was to be made; from which it occurred to me, the observer must have moved his eye up or down the circumference, by means of a ladder or some such contrivance, to rise and lower himself, until he had discovered the altitude of any of the heavenly bodies in their passage over the meridian, so expressed on the arcs of these quadrants; these arcs were very exactly divided into nine large sections; each of which again into ten, making ninety lesser divisions or degrees: and those also into twenty, expressing three minutes each, of about two-tenths of-an inch asunder; so that it is probable, they had some method of dividing even these into more minute divisions at the time of observation.
built perpendicular, and situated, I suppose, in the meridian of the place: a brass pin is fixed at the centre or angle of the quadrant, from whence, the Bramin informed me, they stretched a wire to the circumference when an observation was to be made; from which it occurred to me, the observer must have moved his eye up or down the circumference, by means of a ladder or some such contrivance, to rise and lower himself, until he had discovered the altitude of any of the heavenly bodies in their passage over the meridian, so expressed on the arcs of these quadrants; these arcs were very exactly divided into nine large sections; each of which again into ten, making ninety lesser divisions or degrees: and those also into twenty, expressing three minutes each, of about two-tenths of-an inch asunder; so that it is probable, they had some method of dividing even these into more minute divisions at the time of observation.
My time would only permit me to take down the particular dimensions of the most capital instrument, or the greater equinoctial Sun-dial; represented by A (Fig. 1), which appears to be an instrument to express solar time by the shadow of a gnomon upon two quadrants, one situated to the east, and the other to the west of it; and indeed the chief part of their instruments at this place appear to be constructed for the same purpose, except the quadrants, and a brass instrument that will be described hereafter.
The sketch labelled B in Fig. 1 is another instrument for the purpose of determining the exact hour of the day by the shadow of a gnomon, which stands perpendicular to and in the centre of a flat circular stone, supported in an oblique situation by means of four upright stones and a cross-piece; so that the shadow of the gnomon, which is a perpendicular iron rod, is thrown upon the divisions of the circle described on the face of the flat, circular stone The sketch labelled C in Fig. 1 is a brass circle, about 2 feet in diameter, moving vertically upon two pivots between two stone pillars, having an index or hand turning round horizontally on the centre of the circle, which is divided into 360 parts; but there are no counter divisions on the index to sub-divide those on the circle. This instrument appears to be made for taking the angle of a star yet setting or rising or for taking the azimuth or amplitude of the Sun yet rising or setting.
The use of the instrument (the sketch labelled D in Fig. 1), I was at a loss to account for. It consists of two circular walls; the outer of which is about 40 feet diameter, and 8 feet high; the wall within about half that height, and appear intended for a place to stand on to observe the divisions on the upper circle of the outer wall, rather than for any other purpose; and yet both circles are divided into 360 degrees, each degree being-divided into 20 lesser divisions, the same as the quadrants. There is a door way to pass into the inner circle and a pillar in the centre, of the same height with the lower circle, having a hole in it,
being the centre of both circles and seems to be a socket for an iron rod to be placed perpendicular into it. The divisions on this, as well as all the other instruments, will bear a nice examination with a pair of compass.
being the centre of both circles and seems to be a socket for an iron rod to be placed perpendicular into it. The divisions on this, as well as all the other instruments, will bear a nice examination with a pair of compass.
Figure E is a smaller equinoctial Sun-dial, constructed upon the same principle as the large one A.
I cannot quit this subject without observing that the Bramins without the assistance of the optical glasses had nevertheless an advantage inexperienced by the observers of the more Northern climax. The serenity and the clearness of the atmosphere in the night-time in the East Indies, except at the seasons of the changing the monsoon or periodical winds, is difficult to express to those who have not seen it, because we have nothing in comparison to form our ideas upon: it is clear to perfection, a total quietude subsists, scarcely a cloud to be seen; and the light of the heaven, by the numerous appearance of the stars, afford a prospect both of wonder and contemplation.
This observatory at Benares is said to have been built by the order of the Emperor Ackbar; for as this wise prince endeavoured to improve the arts, so he wished also to recover the sciences of Hindostan, and therefore directed that these such places should be erected; one at Delhi, another at Agra and third at Benares.
Some doubts have arisen with regard to the certainty of the ancient Brahmins having a knowledge in astronomy, and whether the Persians might not have introduced it into Hindostan, when conquered by that people; but these doubts I think must vanish when we know that the present Bramins announce, from the records and tables which have been handed down to them by their forefathers, the approach of the eclipses of the Sun and Moon, and regularly as they advance give timely information to the emperor and the princes in whose dominion they reside. There are yet some remains in evidence of their being at one time in possession of this science. The signs of the Zodiac, in some of their Choultrys on the coast of Coromandel [the East coast], as remarked by John Call, Esq. F.R.S. in his letter to the Astronomer Royal, requires little other confirmation. Mr. Call says, that as he was laying on his back, resting himself in the heat of the day, in a choultry at Verdapetah in the Madura country, near Cape Commorin [Kanyakumari], he discovered the signs of the Zodiac on the ceiling of the choultry: that he found one, equally complete, which was on the ceiling of a temple, in the middle of a tank before the pagoda Teppecolam near Mindurah; and that he had often met with several parts in detached pieces. (See Philos. Trans 1772, p.353). These buildings and temples were the places of residence and worship of the original Brahmins, and bear the marks of great antiquity, having perhaps been built before the Persian conquest. Besides, when we know that the manners and customs of the Gentoo religion are such as to preclude them from admitting the smallest innovation in their institutions; when we also know that their fashion in dress, and the mode of their living have not received the least variation from the earliest account you have of them; it cannot be supposed they would engrave the symbolical figures of the Persian astronomy in their sacred temple, the signs of the Zodiac must therefore have originated; with them, if we credit their tradition of the purity of their religion and customs.
By K. Kesava Rao
Department of Chemical Engineering
Indian Institute of Science
Bengaluru 560012, India
kesava@iisc.ac.in
Department of Chemical Engineering
Indian Institute of Science
Bengaluru 560012, India
kesava@iisc.ac.in
...To be continued ...
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