we see, is upon one side, and a mere assumption. Have I not the same right to assume a similar error in one of the planets, that is, an error of 30', in its radical position, and an error of 1′′ per annum in its motion, so that in 1800 years the error of 30' would be cancelled? Now if this error so assumed be of an opposite nature to the one he assumed, the one cancels the other, and the epoch of the tables would not be at all affected by the circumstance: his conclusion, therefore, in regard to my rule is incorrect; for I do not determine the age of any system of astronomy by a single item, as he thought proper to assume on this occasion, to give the greater plausibility to his assertions; I make use of as many as appear to be the most correct, because the errors counteract each other. Why did he not apply the rule to some tables, the age of which was known to him, the same as I have done in respect of the system of Aryabhatta, in the third section of the second part of my essay, the author of which gives his own date? I have also applied the same rule to the Brahma Siddhanta, the first of the modern astronomical works introduced in A.D. 538, to which the reader may refer, and where he will find the method by which the system was constructed explained at length. The application of the rule, in both these instances, when we had the actual dates of the system before us, demonstrate that it is perfectly just, so far at least as we require Digitized by Google
