in the next place, the nobleman who presided at Montreal is not merely a lord, but a man of very distinguished ability and eminently entitled to the honor from both the character and extent of his original scientific work. His writings, however, are only or chiefly known to scientific men. Numerous papers from his pen are scattered through the pages of the proceedings of several learned societies of England, though some of them have been collected into a volume and published separately. He has produced but one extensive work, namely, "The Theory of Sound," a mathematical treatise in two volumes. It was begun on the Nile in 1872, and published in 1877-78. The article on "Optics," in the last volume of the "Encyclopaedia Britannica," was also written by him. His determinations of the ohm, which were presented to the Paris Conference of Electricians in 1883-'84, have been accepted as the basis of the unit of electrical resistance. His recent experiments in methods of practically measuring the strength of the electric current point to the method, by the deposition of silver, as one capable of furnishing a high degree of accuracy.
To these scanty particulars of Lord Rayleigh's life and career, for which we are mainly indebted to a brief sketch in the Montreal "Star," we may add the estimate of his work given by Sir William Thomson in introducing him to the large audience at the first assemblage of the Association in Montreal, August 27th, when he assumed the presidential chair. Referring first to the work of his predecessor, Sir William Thomson remarked: "Professor Cayley has devoted his life to the advancement of pure mathematics. It is indeed peculiarly appropriate that he should be followed in the honorable post of president by one who has done so much to apply mathematical power in the various branches of physical science as Lord Rayleigh has done. In the field of the discovery and demonstration of natural phenomena Lord Rayleigh has, above all others, enriched physical science by the application of mathematical analysis; and when I speak of mathematics you must not suppose mathematics to be harsh and crabbed. (Laughter.) The Association learned last year at Southport what a glorious realm of beauty there was in pure mathematics. I will not, however, be hard on those who insist that it is harsh and crabbed. In reading some of the pages of the greatest investigators of mathematics one is apt occasionally to become wearied, and I must confess that some of the pages of Lord Rayleigh's work have taxed me most severely, but the strain was well repaid. When we pass from the instrument which is harsh and crabbed to those who do not give themselves the trouble to learn it thoroughly, to the application of the instrument, see what a splendid world of light, beauty, and music is opened to us through such investigations as those of Lord Rayleigh! His book on sound is the greatest piece of mathematical investigation we know of applied to a branch of physical science. The branches of
