of mathematical formulas, and of every note and wave in music the equation lies in the pages of Lord Rayleigh's book. (Laughter and applause.) There are some who have no ear for music, but all who are blessed with eyes can admire the beauties of nature, and among those one which is seen in Canada frequently, in England often, in Scotland rarely, is the blue sky. (Laughter) Lord Rayleigh's brilliant piece of mathematical work on the dynamics of blue sky is a monument to the application of mathematics to a subject of supreme difficulty, and on the subject of refraction of light he has pointed out the way towards finding all that has to be known, though he has ended his work by admitting that the explanation of the fundamentals of the reflection and refraction of light is still wanting and is a subject for the efforts of the British Association for the Advancement of Science. But there is still another subject, electricity and the electric light, and here again Lord Rayleigh's work is fundamental, and one may hope from the suggestions it contains that electricity may yet be put upon the level of ordinary mechanics, and that the electrician may be able to weigh out electric quantities as easily and readily as a merchant could a quantity of tea or sugar. (Applause.) It remains for me only to fulfil the commission which Professor Cayley has entrusted to me of expressing his great regret that his engagements in England prevented his being with us, and in his name to vacate the chair of president of the Association and to ask Lord Rayleigh to take his place as President for 1884. (Applause.) [_Lord Rayleigh then delivered the Presidential Address, a copy of which is appended to this work._] Lord Rayleigh was loudly applauded at the conclusion of his address.