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.