﻿366 C. K. Wead — Time of contact between the 



led me to believe that it would have been impossible for a 

 sheet of ice 1,500 feet or less in thickness to flow across this 

 mountainous region so "utterly regardless, as the great glacier 

 was, of its marked topographical features. 



Geological Laboratory, Indiana University, Bloomington, Ind. 



Aet. XLTI. — On the time of contact between the Hammer and 

 String in a Piano ;* by Charles K. Wead. 



Helmholtz has, as is well known, developed a theory of 

 the action of the hammer on a piano string. If the two remain 

 in contact for a time equal to T \ of the period of vibration of 

 the string, the relative strength of the overtones as computed 

 seems to be about the same as he found in a piano, between the 

 limits C/^33 d. v. and c' = 264 d. v. But in the theory there 

 are several assumptions, and it cannot be confirmed by judg- 

 ments of the ear alone; for we do not yet know certainly, even 

 if Fechner's law be true, what is the proper measure of the 

 stimulus of a sensation; is it the energy of vibration as Helm- 

 holtz assumes, or the square root of it as others have tried to 

 prove, or some less simple function? Further, how is the 

 loudness of a sound, that is, the strength of the sensation, 

 dependent on the pitch of the sound, when several sounds 

 have the same intensity in mechanical measure? Lastly, have 

 we any proof that the relative strength of the component 

 vibrations in the air-wave is the same as in the string? 

 Although the quality of the sound may remain unchanged as 

 the vibration of the string dies away, we have, I believe, abso- 

 lutely no proof that the efficiency of the sounding-board, bridge, 

 etc., is the same for all tones of the scale or for all the over- 

 tones of a given string. 



It has therefore for a long time seemed to me desirable to 

 measure directly the time of contact — an experiment far easier 

 than the settlement of any one of the doubtful questions just 

 referred to. The results of some preliminary measures are, I 

 think, of sufficient interest and accuracy to justify their 

 presentation. 



The method used is quite simple. An electric circuit was 

 completed through a cell, a resistance-box, a galvanometer, a 

 fine wire around the stem of the hammer, a slip of gold-foil 

 (about 20^00 i° cn thick) glued to the face of the hammer, 

 and lastly, the piano wire and frame. The contact between 

 the hammer and string produces a momentary closing of the 

 circuit and a throw of the galvanometer needle, from the 



* Presented before the Am. Assoc. Adv. Science, at the Buffalo meeting. 



