Thomson concludes by showing how, by measuring the non-oscillatory discharge of a condenser (the capacity of which can be calculated) by means of an electrodynamometer and an ordinary galvanometer arranged in series, what W. Weber called the duration of the discharging current may be determined. From this Thomson deduced a value for the ratio of the electromagnetic unit of electricity to the electrostatic unit, and indicated methods of determining this ratio experimentally. This ratio is of fundamental importance in electromagnetic theory, and is essentially of the nature of a speed. According to Maxwell it is the speed of propagation of electromagnetic waves in an insulating medium for which the units are defined. It was first determined in the Glasgow laboratory by Mr. Dugald McKichan, and has been determined many times since. It is practically identical with the speed of light as ascertained by the best experiments. CHAPTER XI THOMSON AND TAIT'S 'NATURAL PHILOSOPHY'--GYROSTATIC ACTION--'ELECTROSTATICS AND MAGNETISM' THE 'NATURAL PHILOSOPHY' Professor Tait was appointed to the Chair of Natural Philosophy in the University of Edinburgh in 1860, and came almost immediately into frequent contact with Thomson. Both were Peterhouse men, trained by the same private tutor--William Hopkins--both were enthusiastic investigators in mathematical as well as in experimental physics, they taught in the sister universities of Edinburgh and Glasgow, and had much the same kind of classes to deal with and the same educational problems to solve. Tait was an Edinburgh man--an old school-fellow of Clerk Maxwell at the Edinburgh Academy--and had therefore been exposed to that contact, in play and in work, with compeers of like age and capabilities, which is one of the best preparations for the larger school and more serious struggles of life. Thomson's early education, under his father's anxious care, had no doubt certain advantages, and his early entrance into college classes gave him to a great extent that intercourse with others for which such advantages are never complete compensation. The two men had much community of thought and experience, and the literary partnership into which they entered was hailed as one likely to do much for the progress of science.