of Edinburgh, Session 1877-78. 
629 
He details liis experiments, and, unlike other observers, extended 
his researches to other metals besides iron. He stretched wires of 
various metals on a sonometer with a helix of wire round them, so 
that he could excite sounds by the simple passage of the current in 
the wire, or by the magnetising action on it of the helix. He used an 
electromotor of five Grove’s cells. He tells us that the sounds emitted 
from iron and other metals, by the direct passage through them of 
a discontinuous current, were in no way different from those 
obtained by magnetisation when the same current was made to 
pass through the helix surrounding the wire. This was especially 
observable in the case of iron. He states also loosely that the 
loudness of the sounds emitted with the same strength of current 
was in proportion to the resistances offered by the wires, and that 
possibly this sounding action had the same conditions as heat in the 
galvanic circuit, so far at least as resistance was concerned. He, 
moreover, states that iron stood quite exceptionally among the metals 
in its power to give out such sounds. 
The exact way in which De la Rive obtained these sounds appears 
to have been lost, for no subsequent observer accords with him. 
Wiedemann, for instance, in his “Electro-Magnetismus,” in keeping 
with the investigations of Wertheim, states that iron alone emits 
sounds under the above conditions, and he quotes De la Rive’s 
remarks on other metals within parentheses. How, the simple 
device of attaching the string of a mechanical telephone to the 
wires when the intermittent current circulates, enables us to observe 
these sounding effects with perfect ease and certainty. When 
attached to a copper wire ("007 inches diameter) the sound is very 
marked; and when to an iron wire (”008) the telephone sounds 
many feet off, the current being that from the five-cell Bunsen 
battery.* Indeed, for the iron wire a telephone is not necessary, 
for the ticking can be heard when the wire is held in the teeth, 
or when it is doubled on the finger and inserted in the passage 
of the ear. There is only one objection to the last mode of pro- 
cedure, viz., that the wire is almost too hot to be comfortable. It is 
not, however, necessary to insert the wire itself into the ear, for a 
cotton thread, tied to the wire and placed in the ear, sounds nearly 
* This was distinctly heard in the auditorium of the Society when the paper 
was read. 
4 o 
VOL. IX. 
