356 Prof. A. M. Mayer’s Experiments on the supposed 
The Table of experiments which I have given is characteristic 
of all of the many series which I have made. In the first column 
(A) I have given the notes of the forks in the French notation, 
which Konig stamps upon his forks. In the second (B) are the 
amplitudes of the vibrations of the end of the fibril im divisions 
of the micrometer-scale; and in column C are the values of 
these divisions in fractions of a millimetre. 
A. B. C. 
Wis Oo dive -0042 millim. 
Wisin ae ar, SO200 ns: 
Mie os, pel Oess Olay” 13, 
nS 0) Params Mees ‘O168-. s 
Dhiei Gesanicecn SP Uo ‘O504, 1S 
Milas on, lor, O26 oe 
NOM cope! tae iG, OL2G ae 
Paes ue al omer, Ol2oe 
ose se es On gs “OVGGr | we 
The superior effect of the vibrations of the Ut, fork on the 
fibril is marked ; but thinking that the differences in the ob- 
served amplitudes of the vibrations might be owing to differ- 
ences in the intensities of the various sounds, I repeated the 
experiment, but vibrated the forks which gave the greater amph- 
tudes of covibration with the lowest intensities; and although I 
observed an approach toward equality of amplitude, yet the 
fibril gave the maximum swings when Ut, was sounded ; and I 
was persuaded that this special fibril was tuned to unison with 
Ut, or to some other note within a semitone of it. The differ- 
ences of amplitude given by Ut, and Sol, and Mi, are con- 
siderable ; and the Table also brings out the imteresting ob- 
servation that the lower (Ut,) and the higher (Ut;) harmonics 
of Ut, cause greater amplitudes of vibration than any interme- 
diate notes. As long as a universal method for the determina- 
tion of the relative intensities of sounds of different pitch re- 
mains undiscovered, so long will the science of acoustics remain 
in its present vague qualitative condition*. Now, not having 
the means of equalizing the intensities of the vibrations issuing 
* T have recently made some experiments in this direction, which show 
the possibility of eventually being able to express the intensity of an aerial 
vibration directly in fraction of Joule’s dynamical unit, by measuring the 
heat: developed im a slip of sheet rubber stretched between the prongs of a 
fork and enclosed ina compound thermo-battery. The relative intensities 
of the aérial vibration produced by the fork when engaged in heating the 
rubber and when the rubber is removed, can be measured by the method I de- 
scribed in the Philosophical Magazine, 1873, vol. xlv. p. 18. Ofcourse, if we 
can determine the amount of heat produced per second by a known fraction of 
