[f. TONO- + -METER.]
1. Music. An instrument for determining the pitch of tones; spec. a tuning-fork, or a graduated set of tuning-forks, as that made by Scheibler about 1833, for determining the exact number of vibrations per second which produce a given tone.
1725. A. Warren (title), The Tonometer, explaining and demonstrating … all the 32 distinct and different Notes, adjuncts or Supplements contained in each of four Octaves inclusive, of the Gamut.
1840. Whewell, Philos. Induct. Sc., I. I. iv. iv. 312. The monochord is a complete and perfect tonometer.
1876. A. J. Ellis, Athenæum, 2 Dec., 731/1. Tonometry was first placed on a scientific basis in a … pamphlet … published at Essen, 1834, and entitled ‘The Physical and Musical Tonometer (Tonmesser), which proves by the pendulum, visibly to the eye, the absolute vibrations of tones,… invented and executed by Heinrich Scheibler.
1881. Broadhouse, Mus. Acoustics, 104. Appunn’s reed tonometer is a mode of measuring the pitch by means of harmonium reeds.
1885. Athenæum, 18 April, 513/3. A class is devoted to … tuning-forks, pitch-pipes, sirens, tonometers, and other appliances for the determination of pitch.
2. An instrument for measuring (a) tension of the eyeball in glaucoma, (b) intravascular blood-pressure, (c) strains within a liquid.
(a) 1876. Catal. Sci. App. S. Kens., § 3674. Tonometer, for Measuring the Hardness and Convexity of the Eye.
1879. P. Smith, Glaucoma, 14. A distinct indication of a different tension was given by the tonometer.
(b) 1898. Allbutt’s Syst. Med., V. 924. If the ventricle of a frog beat in a tonometer under a supply of blood from a pressure bottle, at varying heights, curves may be taken to measure the volume of the ventricle.
(c) 1909. in Cent. Dict. Supp.
Hence Tonometric a., of or pertaining to tonometry; Tonometry, the using of a tonometer; measurement of vibrations of sound or of tension.
1901. Nature, 24 Oct., 630/2. He also presents a *tonometric apparatus, consisting of about 670 diapasons or tuning forks.
1902. Encycl. Brit., XXX. 61/1. At the Philadelphia Exposition of 1876 great admiration was expressed for a tonometric apparatus of his [König’s] manufacture.
1876. *Tonometry [see TONOMETER 1].
1899. Syd. Soc. Lex., Tonometry, measurement of tension, as of the eyeball.
