Page:Lectures on Ten British Physicists of the Nineteenth Century.djvu/65

 heat in the process of conversion, and the heat thus produced becomes dissipated and diffused by radiation and conduction. Consequently, there is a tendency in nature for all the energy in the universe of whatever kind, gradually to assume the form of heat, and having done so, to become equally diffused. Now, were all the energy of the universe converted into uniformly diffused heat, it would cease to be available for producing mechanical effect, since for that purpose we must have a hot source and a cooler condenser. This gradual degradation of energy is perpetually going on; and, sooner or later, unless there be some restorative power, of which we at present have no knowledge whatever, the present state of things must come to an end." Maxwell imagined a restorative process which might be applied by intelligent demons. Suppose a portion of gas to be confined in a closed space, it will have a uniformly diffused temperature. Suppose a partition stretched across with a little door guarded by an intelligent demon. The molecules by their impacts and collisions really have different velocities; what is uniform is the mean velocity. If the demon in charge opens the door so as to let the swift molecules in B go into A, and the slow molecules in A go into B, the degradation of the temperature will be gradually restored.

In 1852 he was married to Miss Margaret Crum, daughter of Walter Crum, Esq. of Thomliebank; a devout lady much attached to the Presbyterian Church. As a consequence, he resigned his fellowship in St. Peter's College; but he was afterwards made an honorary fellow. About this time he organized the first physical laboratory in Great Britain. He had an abundance of experimental problems for his students to tackle particularly on the properties of metals. About four years after Thomson located at Glasgow, submarine telegraphy became an object of practical science. In the working of a submarine cable between England and Holland, it was observed that the signals were more difficult to receive than those from the end of an aerial line. Faraday was the first to investigate the cause of this overlapping of the signals. At first there was a great deal of confusion; speed of signaling was mixed up with velocity