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The early years of his professorship were times of fruitful 
strenuous work. With Joule he established the proposition that 
heat is a form of energy, and that heat and work are mutually 
convertible. On the basis laid by Carnot he applied his powerful 
mind to the principles of heat engines, determined the meaning 
of temperature as a measureable quantity and the principles of an 
absolute scale of temperature, found the absolute zero to be 273 
degrees C, and formulated the two great laws of thermodynamics. 
Thus, by the time he was thirty years of age he had taken the 
leading part in the establishment of the principles governing 
energy and the transformation of energy of universal application. 
From this time Thomson was drawn towards those practical 
applications of science, that gave him a second title to fame. His 
early interest in Fourier’s equations dealing with the flow of heat 
through solids led him to the principles determining the flow of 
electricity along a cable, and to his taking an active part in solving 
the problems involved in the laying of the Atlantic Cable, for which 
he was knighted. He invented for this purpose the mirror gal- 
vanometer and the siphon recorder. Prof. Thomson showed by 
an experiment on the lecture table the sensitiveness of the former 
instrument. From a tiny battery made of a lady’s thimble he 
passed a current through a resistance representing that of several 
Atlantic Cables, when the light from the mirror of the galvano- 
meter instantly responded. About this time, he continued, Sir 
William Thomson (Lord Kelvin) was largely responsible for the 
adoption of the well-known electrical units—the ohm, volt, and 
farad—which have since become of universal usage. With Tait 
he wrote the celebrated ‘‘ Treatise on Natural Philosophy.” From 
Helmholtz’s mathematical investigation on the properties of the 
vortex he was led to propound his vortex theory of atoms, accord- 
ing to which an atom of matter was to be considered a vortex 
in the ether. The lecturer illustrated this by producing vortex 
rings of smoke. Sir William Thomson spent fruitful years of 
research on magnetism, atmospheric electricity, and allied subjects. 
His fondness for yacthing and his skill as a navigator led to his 
improvements of the mariner’s compass, which are now generally 
adopted ; to many improvements in sounding apparatus ; to his 
tide predicting machine, and his mechanical harmonic analyser. 
Very numerous were the instruments and appliances he devised 
for commercial use in electrical measurements. Lantern views of 
many of these instruments were shown on the screen. 
In 1892 Sir William Thomson was made a peer, with the title 
Baron Kelvin, and in 1896 was celebrated at Glasgow his jubilee 
