R. Spice—Sympathetic Resonance of Tuning Forks. 418 
large alteration of period does not imply a large difference in 
length. 
From measurements made with an electro-chemical register- 
ing apparatus, which I designed for this and similar investiga- 
tions, I find that when a fork of the usual dimensions (between 
Ut® and Ut*) is in vibration, its stem or handle alternately rises 
and falls in accord with the period of the fork, through a dis- 
tance of about ;'; inch. When a fork on its case is influenced 
bya distant fork, the case gives the stem this up and down 
motion, which is conveyed to the prongs and sets them in 
vibration after the manner of the hand starting a pendulum 
as specified above. 
steel, hence, retaining similar thicknesses in both cases, an Ut* 
fork in bell-metal would be shorter than an Ut? fork in steel ; 
the ratio of the length of the steel to that of the bell-metal 
tanging as 90: 75. Therefore, though we retain the vibration- 
number, we gain advantage from the shortness of the fork, and 
hence from the increase of angular motion of the prongs 
It was suggested to me that possibly bell-metal had the prop- 
erty of accepting motion more readily than steel. To test this 
point I made a pair of Ut? steel forks, shorter than Koenig's, 
and of course thinner, in order to retain the vibration-number. 
These forks behaved just like the bell-metal forks. Further, I 
made a pair of Ut‘ forks as long as Keenig’s Ut? forks, and of 
“te thicker. These behaved like Koenig’s Ut? forks. Final- 
th taking a Koenig Ut? fork on its case, and one of the short 
aig 7. nded well, whereas on exciting the short fork Koenig’s 
1d Not respond at all. 
230 Bridge st., Brooklyn, July, 1876. 
