Auditory Apparatus of the Culex mosquito. BEY 
from the various resonant boxes, | adopted the plan of sounding 
with a bow each fork with the greatest intensity I could obtain. 
I think that it is to be regretted that Konig did not adhere 
to the form of fork with inclined prongs as formerly made by 
Marloye; for with such forks one can always reproduce the 
same initial intensity of vibration by separating the prongs by 
means of the same cylindrical rod, which is drawn between 
them. Experiments similar to those already given revealed a 
fibril tuned to such perfect unison with Ut, that it vibrated 
through 18 divisions of the micrometer, or *15 millim., while 
its amplitude of vibration was only 3 divisions when Ut, was 
sounded. Other fibrils responded to other notes ; so that [ infer 
from my experiments on about a dozen mosquitos that their 
fibrils are tuned to sounds extending through the middle and 
next higher octave of the piano. 
To subject to a severe test the supposition I now entertained, 
that the fibrils were tuned to various periods of vibration, I mea- 
sured with great care the lengths and diameters of two fibrils, 
one of which vibrated strongly to Ut,, the other as powerfully 
to Ut,; and from these measures I constructed in homogeneous 
pine-wood two gigantic models of the fibrils, the one corre- 
sponding to the Ut, fibril being about 1 metre long. After a 
little practice I succeeded in counting readily the number of 
vibrations they gave when they were clamped at one end and 
drawn from a horizontal position. On obtaining the ratio of 
these numbers, I found that it coincided with the ratio exist- 
ing between the numbers of vibrations of the forks to which 
covibrated the fibrils of which these pine-rods were models. 
The consideration of the relations which these slender, taper- 
ing, and pointed fibrils must have to the aérial pulses acting on 
them, led me to discoveries in the physiology of audition which 
I imagine are entirely new. If a sonorous wave falls upon one 
of these fibrils so that its wave-front is at right angles to the 
the intensity, we have the amount produced by the vibration with its entire 
iutensity. Then means can be devised by which the aérial vibration pro- 
duced by this fork can always be reproduced with the same imtensity. 
This intensity, expressed in fraction of Joule’s unit, is stamped upon the 
apparatus, which ever afterward serves as a true measure for obtaining the 
intensities of the vibrations of all simple sounds having the same pitch as 
itself. The same operation can be performed on other forks of different 
pitch ; and so a series of intensities of different periods of vibration is ob- 
tained expressed in a corresponding series of fractions of Joule’s unit. 
Recent experiments have given —_* — of a Joule’s unit as the approxi- 
mate dynamic equivalent of ten seconds of aérial vibrations produced by 
an Ut, fork set in motion by intermittent electromagnetic action and placed 
before a resonator. 
Ann. & Mag. N. Hist. Ser. 4. Vol. xv. 25 
