316 Lord Rayleigh : Acoustical Notes. 



the heat generated by the " j3 particles " would not get into 

 the calorimetric water, but would be lost in heating the outer 

 air around it. If, in the arrangement of § 8, the globe were 

 only half a centimetre instead of fifty centimetres radius, a 

 considerable proportion of the " j3 particles " would get away 

 without leaving their energy in the lead or water, but prac- 

 tically all the " a particles " that get out of the Radium would 

 be stopped by the lead, and would give up their energy to it. 



§ 12. The dimensions stated in § 8 are chosen merely for 

 the sake of illustration, and are not suggested as suitable for 

 any practical experiment. 



§ 13. The words " radiated " and " radiation" printed in 

 italics in § § 3, 7, and 8, above, indicate what seems to me 

 the only possible way of escaping the conclusion that Radium 

 •contains a quasi-infinite supply of energy, which can be 

 •drawn upon for hundreds of years, without any compensating 

 extraneous source. It seems to me not absolutely impossible 

 that Radium may be, as it were, an exceedingly black body, 

 relatively to waves of ether so short that lead and other solid 

 and liquid substances are transparent for them. 



h 



XXIV. Acoustical Notes. — VII. 

 By Lord Rayleigh, O.M., Pres. E.S. 



[Plate VIII.] 



Sensations of Right and Left from a revolving Magnet and 

 Telephones. — Multiple Harmonic Resonator. — Tuning-Forks with slight 

 Mutual Influence. — Mutual Reaction of Singing Flames. — Longitudinal 

 Balance of Tuning-Forks. — A Tuning-Fork Siren and its Maintenance. — 

 Stroboscopic Speed Regulation. — Phonic Wheel and Commutator. 



Sensations of Right and Left from a revolving Magnet 

 and Telephones. 



AMONG the methods available for the production of a pure 

 tone in a telephone circuit is that where the electromotive 

 force has its origin in the revolution of a small magnet about 

 an axis perpendicular to its length, the magnet acting 

 inductively upon a neighbouring coil which forms part of 

 the telephone circuit. It was by experiments made partly 

 in this manner that I formerly f determined the minimum of 

 current necessary for audibility in the telephone. In 

 connexion with recent work upon the origin of the lateral 

 sensation in binaural audition % I have again employed this 



* Communicated by the Author. 



t Phil. Mag. xxxviii. p. 285 (1894) ; Scientific Papers, iv. p. 109. 



J Phil. Mag. [6] xiii. p. 214 (1907). 



