48 Dr. A. Elsass on a new 
while (ii.) becomes 
T'x ABC=area ABC(OG +2) A. iG 
The method here shown of considering separately the 
equilibrium first of vertical and then of horizontal forces is 
equally applicable to sessile drops and to portions of liquid 
raised by adhesion to a base, and brings out very clearly 
many results which have hitherto usually been obtained as 
special cases by rather complicated processes of integration. 
Clifton College, Oct. 27, 1884. 
V. On a new Form of Monochord. 
By Dr. A. Etsass of Marburg”. 
FHXHE monochord has been employed from time immemorial 
to demonstrate the laws of transverse vibrations. It is used 
to show that, in producing its fundamental note, a string 
vibrates in its whole length, but that, in producing the higher 
partial tones, nodes are formed; and by its means the law of 
Mersenne can be demonstrated, according to which the fun- 
damental note of a string depends upon its length, its tension, 
and its mass. In recent times Melde’s apparatus has also 
been employed to show the mode of vibration of the string, 
which by its means may be made evident to a large audience. 
The essential parts of this apparatus are a tuning-fork and 
a stretched yielding thread, one end of which is attached to the 
tuning-fork. If the tuning-fork is made to sound, its vibra- 
tory motion induces a transversal vibration of the thread, 
both when the motion of the tuning-fork takes place at right 
angles to the thread and when it takes place in the direction 
of its length and the magnitude of the vibrations of the 
thread is so great that they can be observed from some dis- 
tance off. The present communication describes a new form 
of vibration-apparatus which combines the advantages of the 
monochord and of Melde’s apparatus. 
In Melde’s apparatus the thread is made to assume different 
forms of vibration by altering its tension, and with it the ratio 
of its oscillation-period to that of the body which produces the 
motion; but the oscillation-period itself, which depends upon 
the period of the exciting body, is not subject to variation. 
In the arrangement to be described, however, all variations 
can be obtained with the same thread by altering the period 
of the exciting body, so that the law connecting the normal 
* Translated from the Zettschrift fii Instrumentenkunde for October 
1824, frcm a separate impression communicated by the Author. 
