Page:Lectures on Ten British Physicists of the Nineteenth Century.djvu/21

 he continued the practice. While he was very skillful as an experimenter, he was not so successful as an expositor. He had received no training as a teacher; following the example of his father he was accustomed to present things after a curiously grotesque fashion; his vision was short-sighted; his speech was not free from hesitation; his imagination outran his vocabulary; and he could not easily put himself at the viewpoint of the average student attending his lectures.

During the next year he was married to Katherine Dewar, daughter of the principal of the college and a Presbyterian divine, sister I believe of James Dewar who in recent years has become famous for his investigation of the properties of bodies at temperatures bordering on the absolute zero.

St. John's College, Cambridge, had founded an Adams prize in honor of the discoverer of Neptune, to be awarded to the writer of the best essay on a prescribed subject, and to be open to all graduates of the University. In 1857 the examiners chose for the subject "The motion of Saturn's rings." Maxwell made an elaborate investigation, and his essay carried off the prize.

Galileo in 1610 by means of his small telescope discovered a pair of satellites attached to the planet, one on either side. Huyghens in 1659 resolved the pair of satellites into a continuous ring. Cassini in 1679 resolved the continuous ring into an outer and inner ring. Herschel in 1789 determined the period of rotation of the outer ring. In 1850 a dusky ring within the inner bright ring was discovered by Bond at Cambridge, Mass. Maxwell opens his essay as follows: "When we contemplate the rings of Saturn from a purely scientific point of view, they become the most remarkable bodies in the heavens, except, perhaps those still less useful bodies the spiral nebulæ. When we have actually seen that great arch swung over the equator of the planet without any visible connection, we cannot bring our minds to rest. We cannot simply admit that such is the case, and describe it as one of the observed facts in nature not admitting or requiring explanation. We must either explain its motion on the principles of mechanics