A logarithmic treatment of light propagating through a uniform medium. John Keill was an Edinburgh native who earned distinction under David Gregory in mathematics and natural philosophy there, and who followed him to Oxford in 1691, where, like Gregory, he made a name for himself as an enthusiastic vindicator of Sir Isaac Newton. At Balliol College he demonstrated by experiments the validity of some of the chief propositions of Newton concerning light and colour, among other things. Oddly, John Keill had been one of the witnesses against Gregory back at Edinburgh, during the famous Visitation that had prompted him to apply for the Savilian Chair at Oxford.