State of Experimental Acoustics. 301 



As to (3), I showed some years ago* that, on certain sup- 

 positions which cannot be very far from the truth, the energy 

 of notes of different pitch and the same loudness varies as the 

 wave-length. The other conclusions drawn at that time were 

 based on the supposition that mechanical intensity was a true 

 measure of the impression on the sense. The arrangements 

 now described will furnish the means of examining this point 

 in other ways. 



(4) When sounds of different pitch excite different parts of 

 the sensorium, it appears probable that Fechner's law applies 

 to each part separately. It is quite certain that a single soft 

 stop sounding the octave below is detected at once, if added to 

 the full organ without such stops ; whereas the addition of a 

 similar stop, having the same pitch as any part of the sound 

 actually present, could not be detected by the most experienced 

 ear. This part of the investigation is as yet untouched. 



Phonograph and Phonautograph. 



These instruments consist of devices for producing marks 

 characteristic of sounds on a moving surface, generally a cy- 

 linder which rotates uniformly. The uniform motor will give 

 to the results of these instruments a completeness which they 

 now generally fail to possess. It has hitherto been almost 

 impossible to obtain, for instance, phonographic records of 

 musical sounds, on account of the uncertainty of the speed of 

 rotation ; and the exact reproduction of such sounds from the 

 phonograph has presented great difficulties, if, indeed, it has 

 ever been accomplished. 



The most interesting applications of the phonograph, how- 

 ever, are to the analysis of speech. The forms corresponding 

 to different vowels have been determined by Messrs. Jenkin 

 and Ewing ('Nature,' xviii. pp. 167, 340, 394, 454). But 

 the point in which the proposed arrangements will be of most 

 value is in the analysis of the inflections of speech, or the rapid 

 variations of pitch which occur continually. This analysis is 

 of the highest importance for phonology, as the inflections are 

 undoubtedly among the principal characteristics of dialects. 

 The employment of the uniform motor in connexion with these 

 recording instruments promises the easy solution of this 

 problem. 



observation of " Tom " is by no means final ; besides the disturbing influ- 

 ence of buildings, &c, a light breeze got up at the time of the distant ob- 

 servation. But the determination seems worth quoting; indeed it can- 

 not, I think, be very far wrong. 

 * Phil. Mag. 1872, xliv. p. 381. 



