The investigations of the late Sir Charles “Wheatstone on the subject of the powers of resonance of different masses of air enclosed in chambers of certain definite simple forms, were brought before us by Professor Adams in 1876, and it appeared to me that it might be a matter of interest to this Association to enter briefly upon the consideration of the resonance of brass wind instruments as illustrating Wheatstone's laws. There is very commonly a vagueness used in the description of such instruments which I submit is misleading; they being usually considered to be cones, or cones combined with cylindrical tubing, neither of which descriptions properly applies. And farther, they are commonly considered to be of necessity in tune, that is, in just intonation, having the vibrational numbers of the notes that may be produced from them without altering their length, in the proportion of the numbers, 1, 2, 3, &c. As so great an authority as Prof. Helmholtz writes (‘Sensations of Tone,’ pp. 511, 641): ‘Horns and trumpets have already naturally just intonation,’ and ‘brass instruments naturally play in just intonation, and can only be forced to the tempered system by being blown out of tune,’ it seemed to me worth attention that this must be taken only as being particularly, and not generally true: that is, that though the ideal brass instrument has such characteristics, this ideal is not necessarily attained to in practice. The relative and absolute numbers of vibrations of the first eight tones required on a brass instrument, taking the 4 feet C of 128 vib.