Indian Science and Technology in the Eighteenth Century: Some Contemporary European Accounts c10.8

c10.8

It is well known that the problems of finding the precession of the equinoxes, and the mutation of the earth’s axis, have been considered by some of the most learned mathematicians, and yet they are not agreed concerning it: Some great authors as Newton, Simpson, Walmsley and Sylvain Bailly, supposed the action of the sun and moon to bring the equator out of its place, and to make it revolve round the old axis in a different position; while others as d’Alembert, Euler, La Grange and Titius, suppose the result to be a new equator and a new axis. This last seems indeed to be partly the case, for we cannot otherwise account for equatorial productions being found in Russia and Siberia; nor how those of the frozen zone should be found in the torrid: The matter however is still very doubtful, and requires the aid of observations; for in my opinion even those that have treated the subject best, have omitted some parts that are very essential; for some of them have made a wrong estimation of the quantity of the solar force and all of them have assumed the rigidity of the protuberant parts of the earth’s equator, in their calculations; which is evidently contrary to fact; because we know that near 5/6th of the whole equator is covered with water; and there are not even signs of shallows any where in it, to speak of, except in the short distance between Madagascar and Sumatra: This must make so great a difference in the result that it scarcely seems possible to determine the matter alone by theory: The fact however is certain, that the best mathematicians differ greatly in their conclusions; but if the earth acquires a new axis the meridians will consequently be changed; and if the Quadrant at Benares was placed in the plane of the meridian when the building was erected, it cannot be in the plane of the meridian now; and therefore if the quantity of its deviation from that plane, be carefully and accurately determined it may answer many useful purposes in astronomy, and likewise be serviceable when the theory is perfect to point out the time when the observatory was built, exclusive of its use in the mutation and precession.