Page:Lectures on Ten British Physicists of the Nineteenth Century.djvu/74

 a Fourier series is obtained by mechanical means. The tides for a given part for a whole year can be wound out of it in four hours, thus facilitating their prediction to an extraordinary degree. The form in which it gives the prediction being a continuous curve on paper, it enables the height of the water at any moment to be ascertained by inspection, while any arithmetical result that could possibly be worth the trouble of calculating, would only give the times of high and low water."

Sir William Thomson was for many years a member of the Committee of the British Association, which had in charge the development of an absolute system of units. He was the champion of the centimeter as opposed to the metre; and his argument was that it was important that the density of water should be unity, not 1,000,000. Electrical measurement was then in its infancy. Looking at the question in the light of recent development, we see that the adoption of the centimeter was a mistake for the desired system of C.G.S. electric units is too small for practical purposes, and the actual system which is used involves the fundamental units multiplied by some power of ten. Hence electrical computations now include the metric system proper, the C.G.S. system, and the practical electric system. Sir William Thomson designed many instruments for the purpose of electrical measurements, and for the manufacture of these instruments established a large workshop in Glasgow, under the management of James White. This has been a principal source of his fortune.

When I was at work in Tait's laboratory, Sir William Thomson was president of the Royal Society of Edinburgh; and I have often heard him read papers and make addresses. These meetings brought him to Edinburgh frequently, and it was his custom to visit the laboratory of his colleague Tait. He must originally have been about six feet high. But for many years his height has been diminished by a stiff leg which was brought about in the following way. He broke his leg when skating on the ice, and would not remain at rest until it had recovered properly. Otherwise his appearance was athletic. Compared with Tait, he was not so elegant a speaker, but his