itself with the means of reconcentrating its physical energies, and renewing its activity and life. For aught we know, these opposite processes may go on together, and some of the luminous objects which we see in distant regions of space may be, not stars, but foci in the interstellar ether."
In 1853 Rankine was elected a Fellow of the Royal Society of London; and in the following year he sent to that Society one of his important memoirs "The geometric representation of the expansive action of heat."
Glasgow University was in advance of the Edinburgh University in having a chair of civil engineering and mechanics. At the beginning of 1855 the incumbent of the chair was incapacitated by ill health, and Rankine acted as substitute for the remainder of the session. That same year at the age of 35 he was appointed to the chair.
Professor Rankine has been described by an intimate friend, Professor Tait: "His appearance was striking and prepossessing in the extreme, and his courtesy resembled almost that of a gentleman of the old school. His musical tastes had been highly cultivated, and it was always exceedingly pleasant to see him take his seat at the piano to accompany himself as he sang some humorous or grotesquely plaintive song words and music alike being generally of his own composition. His conversation was always interesting, and embraced with equal seeming ease all topics, however various. He had the still rarer qualification of being a good listener also. The evident interest which he took in all that was said to him had a most reassuring effect on the speaker, and he could turn without apparent mental effort from the prattle of young children to the most formidable statement of new results in mathematical or physical science, when his note-book was at once produced, and in a few lines he jotted down the essence of the statement, to be pondered over at leisure, provided it did not at once appear to him how it was to be modified. The questions which he asked on such occasions were always almost startlingly to the point, and showed a rapidity of thought not often met with in minds of such caliber as his, where the mental inertia which
