162 Scientific Intelligence. 



eclipse of Aug. 7. Professor Mayer was placed in charge of the 

 expedition, and made a large number of successful photographs. 

 In 1871, he was called to the professorship of Physics in the 

 Stevens Institute of Technology, which position he held until the 

 close of his life. 



Professor Mayer was an enthusiastic and active investigator, 

 and a prolific writer upon scientific subjects. He had the com- 

 mand of a clear and graceful style, and possessed in a remarkable 

 degree the power of presenting scientific subjects in a per- 

 spicuous and interesting manner. He made numerous contribu- 

 tions to various journals, cyclopsedias, and other scientific publi- 

 cations, but the memoirs in which he embodied the results of his 

 own researches were chiefly published in the American Journal of 

 Science. His papers published in this Journal, since 1870, number 

 forty-seven titles, covering nearly four hundred closely printed 

 pages, not counting various notes and minor contributions. While 

 embracing a great variety of topics in physics, his studies were 

 more actively pursued in the . departments of electricity and 

 electro-magnetic phenomena, in optics, especially photometry and 

 color-contrasts, but more particularly in acoustics, which was a 

 favorite field of research, in which his discoveries gave him 

 the prominence and authority of a specialist. His acoustical 

 researches form a connected series of papers, in ten numbers, 

 amounting to nearly one half the total volume of his contribu- 

 tions. The following somewhat abbreviated titles will indicate 

 their purport : — The translation of a vibrating body causes it to 

 give a wave-length differing from that produced by the same 

 vibrating body when stationary (1872): a method of detecting 

 the phases of vibration in the air surrounding a sounding body ; 

 and thereby measuring directly in the vibrating air the length of 

 its waves and exploring, the form of its wave-surface, resulting in 

 the invention of the topophone (1872): a simple and precise 

 method of measuring the wave-lengths and velocities of sound 

 in gases ; and on an application of the method in the invention of 

 an acoustical pyrometer (1872): the experimental determination 

 of the relative intensities of sounds ; the measurement of the 

 powers of various substances to reflect and to transmit sonorous 

 vibrations (1873) : experimental confirmation of Fourier's 

 theorem; experimental illustration of Helmholtz's theory of 

 audition; experiments on the supposed auditory apparatus of 

 the mosquito, in which it is shown that the fibrils of the 

 antennae of the male mosquito vibrate sympathetically to sounds 

 having the range of pitch of sounds emitted by the female 

 mosquito ; suggestions as to the function of the spiral scale of the 

 Cochlea ; six experimental methods of sonorous analysis ; curve 

 of musical note formed from six sinusoids of the first six harmon- 

 ics ; curves for various consonant intervals ; experiments in 

 which motions of a molecule of air are derived from these for six 

 elementary vibrations of a musical note (1874) : determination of 

 the law connecting pitch of sound with the duration of residual 



