Popular Science Monthly/Volume 10/December 1876/Sketch of Professor Mayer
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Sketch of Professor Mayer
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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 described in a paper in the American Journal of Science and Arts, entitled "A New Apparatus for the Determination of Carbonic Acid," which was republished in Germany. His second paper was on the estimation of weights of very small portions of matter, in which he showed that, by the deflections of fine glass fibres, we can weigh a particle of matter as small as the 1000 of a milligramme. While at the Lehigh University, he designed and superintended the erection of an astronomical observatory, put together and adjusted the instruments, and made a series of observations on the planet Jupiter, which were republished in England. He was in charge of the party sent by the United States Government to observe the eclipse of the sun at Burlington, Iowa, August 7, 1869, and took forty-one perfect photographs of the eclipse with exposures lasting only the 500 of a second.
While at the Lehigh University, Prof. Mayer contributed to the American Journal of Science and Arts and the Journal of the Franklin Institute various original contributions on the "Solar Protuberances," "Spectral Analysis of the Stars," "Physical Constitution of the Sun," "Electro-Magnetism," "Electric Conductivities," "On the Alleged Electro-Tonic State," "Magnetic Declination in Connection with the Aurora," "Photographing the Magnetic Spectra;" and at the Salem meeting of the American Association he read an instructive paper "On the Thermo-Dynamics of Waterfalls." He had taken the temperatures of the water at Trenton and Niagara before it leaps the cataract and after it strikes below. According to theory, when the falling motion is arrested, it is converted into heat, and should be shown in a rising temperature below. The observations indicated that the effects of evaporation and contact of the divided water with the air were greater than the impact in changing the temperature of the fallen water, so that it may be actually colder below than above. But on days when the air is saturated with moisture, and the temperatures of the water and air are about the same, results were obtained which show that the warming of the falling water conforms to Joule's law of the conversion of motion into heat.
Since entering upon his duties at the Stevens Institute of Technology, notwithstanding the labor of lecturing and teaching which the position involves, Prof. Mayer has conducted elaborate investigations in various branches of physics, which have given to science many new and important results. Among these may be mentioned researches in magnetism, heat, and especially "On the Effects of Magnetization in changing the Dimensions of Iron and Steel Bars," and "On the Isothermals of the Solar Disk." We cannot here give the particulars of these interesting inquiries, but must refer the reader to the memoirs in the scientific journals.
The line of investigation, however, to which Prof. Mayer has mainly devoted himself within the last few years is that of acoustics in its various physical connections, and especially in relation to the theory of music. These researches are described in papers contained in the American Journal of Science and Arts, and several of his important conclusions have been incorporated in the English edition of Helmholtz's “Sensations of Tone as a Physiological Basis for a Theory of Music.” Mr. Alexander J. Ellis, F. R. S. (the translator of the above work), has also recently published a lecture which he delivered before the London Musical Association, on the application of Prof. Mayer's discoveries to the elucidation of the fundamental principles of musical harmony.
The chief claims of Prof. Mayer in regard to his recent acoustical results may be concisely summed up as follows:
1. He discovered that, by using the phenomena of sympathetic vibration, one can show that the translation of a vibrating body causes it to give sonorous waves, differing in length from those produced by the same vibrating body when stationary.
2. He first succeeded in actually detecting the different phases of vibration in the air surrounding a sounding body, and thereby measured the lengths of its waves; and first experimentally explored in the free air the exact form of any wave-surface; and he has determined the forms of these envelopes around a sounding body with as much facility as one can obtain the form of the surface of a palpable body in the dark.
3. He devised a simple and accurate method of measuring the wave-lengths of sound in air and in gases, and was the first to measure with precision the relative intensities of sounds by means of manometric flames.
4. He first approximately determined the mechanical equivalent of an aërial sonorous vibration.
5. He obtained in an experiment all the conditions required in “Fourier's theorem,” and thus first gave an exact experimental confirmation of it.
6. He has devised and used five new methods of sonorous analysis for the decomposition of a compound sound into its elementary simple tones. He also first, by means of a rotating disk, reproduced the vibratory motions of a molecule of air, when it is animated with the resultant action of the six elementary vibrations forming a musical note.
7. He first discovered, by delicate experiment, that the fibrils of the antennæ of the male mosquito vibrate sympathetically to notes which have the range of pitch of the sounds given out by the female mosquito. He also showed first how an insect may determine the direction of sounds by means of his antennæ.
8. He discovered that the terminal auditory nerve-fibrils vibrate half as often in a given time as the membrane of the tympanum and the ossicles of the ear, and proposed on these facts a new hypothesis of the mode of audition.
9. He first discovered the law connecting the pitch of a sound with the time that the sensation of the sound endures after the air has ceased to vibrate the tympanic membrane. This law rendered the qualitative results of Helmholtz quantitative; and in the third edition of Helmholtz's “Tonempfindungen” Mr. Alexander J. Ellis, as noted above, has extensively used this law as the only basis for reaching exact quantitative results in the fundamental phenomena of musical harmony. This law Prof. Mayer has applied extensively to the elucidation of the fundamental facts of harmony, and to the explanation of many obscure phenomena in the physiology of hearing.
10. He discovered that sonorous sensations interfere with one another, and that, although a low sound may entirely obliterate the sensation of a sound higher in pitch, yet a sound cannot in the slightest obliterate the sensation of another sound lower than it in pitch. He has made applications of these discoveries in showing that a radical change is required in the usual method of conducting orchestral music, and in a new method of determining the relative intensities of sounds.
11. He has determined with great precision the laws of the vibrations of tuning-forks, especially in the direction of the bearing of these laws on the action of chronoscopes used in determining the velocities of projectiles. He first accurately gave the correction to be applied in all such determination on account of the different temperatures of the forks.
Besides these difficult and delicate original investigations, Prof. Mayer has contributed numerous articles to Appletons' and Johnson's “Cyclopædias” in his more especial lines of inquiry, and has written much for various popular publications. He was one of the editors of the American Journal of Science and Arts, but reluctantly gave up its duties in 1873 on account of weakness of sight. He then suspended work, and went to England for a vacation, where he was cordially received and kindly entertained by his brethren of the various scientific societies.