Gentlemen,—It is now nearly five-and-forty years since I first opened my lips in this Society, a venturous young man, undertaking to instruct both practical men and men of science, as well as the public at large, all at the time keenly interested in the inquiry,—What were the principles for properly constructing burners for combustion of the light-giving gases? What the relative values of oil gas and coal-gas for giving out light, and which of the two should thenceforth be used for illuminating the world? At that time it was assuredly the farthest thing of all from my dreams that a period might come round when, by the voices of my Fellow-Members, I should be promoted to an office, the highest in learning or science, as the case may be, which Scotland can offer to their votaries,—held last by Sir David Brewster, and previously filled by the Duke of Argyll, Sir Thomas Brisbane, Sir Walter Scott, and Sir James Hall.