names, the Public would allow that, by their discernment and abilities, they are fully entitled to the confidence which I have placed in them. In the progress of the work, I became sensible of my own deficiency with respect to another point. In order to give an accurate idea of the imperfection both of the theory and practice of navigation among the Ancients, and to explain, with scientific precision, the manner in which they ascertained the position of places, and calculated their longitude and latitude, a greater portion of mathematical knowledge was requisite, than my attention to other studies had permitted me to acquire. What I wanted, the friendship of my ingenious and respectable Colleague, Mr. Playfair, Professor of Mathematics, has supplied; and I have been enabled by him to elucidate all the points I have mentioned, in a manner which, I am confident, will afford my readers complete satisfaction. To him, likewise, I am indebted for the construction of two maps necessary for illustrating this Disquisition, which without his assistance I could not have undertaken. I HAVE adhered, in this work, to an arrangement I followed in my former compositions, and to which the public has been long accustomed. I have kept historical narrative as much separate as possible from scientific and critical discussions, by reserving the latter for Notes and Illustrations. I flatter myself that I may claim, without presumption, the merit of having examined with diligence what I submit to public inspection, and of having referred, with scrupulous accuracy, to the authors from whom I have derived information. COLLEGE OF EDINBURGH, May 10th, 1791. CONTENTS. Intercourse with India, from the Conquest of Egypt by the Mahomedans, to the Discovery of the Pas- sage by the Cape of Good Hope, and the Esta- |