(b. Montjoie, near Aix-la-Chapelle, Nov. 11, 1777 ; d. Nov. 20, 1838), a silk manufacturer who, after many travels, settled down a t Crefeld, where he was first - assistant Burgermeister. He made some interesting experiments with J e w 's - h a r p s (q.v.), and in 1812-13 turned his attention to the imperfections of existing means of tuning. He first tried a monochord, but finding th a t he could not always get the same note from the same division of his monochord, he endeavoured to help himself by beats, and discovered th a t each beat corresponded to a difference of two simple vibrations or one double vibration in a socond. His plan was to fix the monochord by finding the stopped length which would give a note beating four times in a second with his own fork. Then, after endless trials and calculations, he found similar places for all the divisions of the scale, and finally from the monochord made forks for each note of the equally tempered scale. By repeated comparisons with his forks he found th a t it was impossible to make a mathematically accurate monochord, or to protect it from the effects of temperature. He then h it upon the plan of inserting forks between the forks of his scale, from the lowest A of the violin to the open A, and counting the beats between them. I t was this counting th a t was the trouble, but by highly ingenious mechanical contrivances he was enabled to complete the count of his fifty-two forks within from -0067 to 00083 beats or double vibrations in a second, and hence to tune a set of twelve forks so as to form a perfectly equal scale for any given pitch of A. The particulars of his forks and the mode of counting them are contained in his little pamphlet Der physikalische und musikalische Tonmesser (Essen, Badeker, 1834, p. 80, with lithographic plates),1 from which the preceding history has been gathered. During his life- 1 The physical and musical Tonometer, which proves visibly, by means of the pcndulum, the absolute numbers of vibrations of musical toner, the principal kinds of combinational tones, and the most rigid exactness of equally tempered and mathematical ju s t chords. time he issued four smaller tracts, showing how to tune organs by beats, w'hich were collected after his death as H. Scheibler's Schriften, etc. (Crefeld, Schmiiller, 1838). These pamphlets form p a r t of the interesting bequest left to A. J . Hipkins by A. J . Ellis, and have since completed Hipkins's gift to the Royal Institution in memory of his friend Dr. Ellis. Scheibler's wonderful tonometer of fifty-two forks has completely disappeared. But another one, of fifty-six instead of fifty-two forks, which belonged to Scheibler, still exists, and was inherited by his daughter and grandson, who lent i t to Amels, formerly of Crefeld, who again lent i t to A. J . Ellis, who counted it and, having checked his results by means of M'Leod's and Mayer's machines for measuring pitch, gave the value of each fork in the Journal o] the Society of Arts for Mar. 5, 1880, p. 300, correct to less th an one-tenth of a double vibration. The two extreme forks of this fiftysix- fork tonometer agree in pitch precisely with those of the fifty-two-fork tonome ter; but no other forks are alike, nor could the forks of the fifty-two-fork tonometer have been easily converted into those of the other one. In 1834, a t a congress of physicists a t Stuttgart, Scheibler proposed with approval the pitch A 440 a t 69