PHYSICS. 221 



showed a remarkable concordance, the extreme measure- 

 ments in the worst set of observations on a fork of 256 com- 

 plete vibrations only differing by 0.005 per cent., while in 

 the good set they agreed within 0.00078 per cent. The new 

 series from 256 to 512 he found to give from 0.3 to 0.5 of a 

 vibration more than was anticipated, but this he ascribes to 

 difference of temperature. 



Ellis, who some months ago questioned the accuracy of 

 Eonig's forks, has made more experiments with Appun's 

 tonometer, upon the indications of which he based his state- 

 ment, and finds (1) that the beats of the harmonium reeds 

 in Appun's tonometer are affected by taking place in a con- 

 fined space of air ; (2) that they are accelerated ; and (3) 

 that the acceleration, being roughly about one per cent., will 

 probably, when completely ascertained, account for the dis- 

 crepancy observed. The acoustic fact thus ascertained has 

 undoubtedly important bearing on other similar phenomena. 



Dubois has studied the vibrations of tuning-forks by 

 means of vermilion, which is mixed with water and placed 

 on the branches of the fork. When these are vibrated, stria) 

 are produced, and the vermilion gives a figure by settling 

 in the grooves. In the case of open pipes, a band of paper 

 charged with the vermilion was placed over the opening. 

 He finds (1) that two sounds of the same pitch but of differ- 

 ent instruments give the same stria?, and (2) two sounds of 

 different pitch give stria) inversely proportional to the num- 

 ber of vibrations of the sounds. The same results were ob- 

 tained with vibrating plates. 



Ellis has communicated to Nature a correspondence he 

 lias had with Cavaille-Coll, the celebrated organ-builder of 

 Paris, on the general question of musical pitch. He has in 

 his possession one of Scheibler's tonometers a series of fif- 

 ty-six forks, varying from A 220 to A 440 double vibrations, 

 by four beats. Their extreme accuracy is shown by the fact 

 that the 400-vibration fork was found to be in unison with 

 Foucault's mirror, determined by him to rotate exactly 400 

 times a second. With reference to the Cagniard de Latour 

 siren, the present usefulness of it depends upon two im- 

 provements of Cavaille-Coll first, the regulator by which 

 the wind pressure is preserved constant, and, second, the au- 

 tomatic counter. On comparing the French normal diapa- 



