Page:Popular Science Monthly Volume 10.djvu/242

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that only motion can breed motion, energy means motion; and that as such its amount is constant, and its presence, behind whatever veil, continuous; so that it is only properly divisible into two kinds, perceptible and imperceptible.



AMONG the younger physicists of the country who have done honor to American science by the interest and extent of their original researches, the subject of the present sketch, and of whom we give an excellent portrait this month, holds a distinguished place. Though now only in the prime of his manhood, he has already made many refined and elaborate experimental researches, by which he is widely and favorably known to men of science both in this country and in Europe.

Alfred Marshall Mayer was born in Baltimore, November 3, 1836. His grandfather, Christian Mayer, was descended from an ancient family in the city of Ulm, Würtemberg, and came to Baltimore when a young man. Here he made a large fortune in trade with India and Mexico. He was well known in his day for his liberal and elegant hospitality, his extensive reading, profound knowledge of mercantile law, and those marked social and gentlemanly traits that made him a delightful companion. His father was Charles F. Mayer, who was distinguished for his learning, eloquence, and extensive literary culture. He is the nephew of Brantz Mayer, a prominent writer, who is especially known by his various valuable works on Mexico, where he resided for a time as secretary of legation.

Prof. Mayer was partly educated at St. Mary's College, in Baltimore, which he left at the age of sixteen for a more practical sphere of study. He entered the workshop) and draughting-room of a mechanical engineer, where he remained two years, acquiring a knowledge of the use of tools, mechanical drawing, the method of constructing machines, and careful mechanical manipulation. Subsequently, during two years, he cultivated analytical chemistry by thorough laboratory practice.

Prof. Mayer has occupied the chair of Physics, with Chemistry and Astronomy, in several colleges, as follows: University of Maryland, 1856-'58; Westminster College, Missouri, 1859-'61; Pennsylvania College, Gettysburg, 1865-'67; Lehigh University, Bethlehem, Pennsylvania, 1867-'70; and the Stevens Institute of Technology since 1871. In 1863-'64 he studied physics, mathematics, and physiology, in the University of Paris.

Prof. Mayer's first contribution to science was made in 1855, and