636 Proceedings of the Royal Society 
the latter position there was a pronounced tendency to push and 
pull. 
I adopted a similar arrangement with the vibrating disc of the 
telephone. To the middle of one T cemented an india-rubber tube 
to act as a yielding handle, and the paper telephone wire was sol- 
dered near the middle. The disc w T as made to move in front of a 
telephone core excited by the coil just named. The movements of 
the disc were very violent, and made in all directions, making the 
conuecting string jingle loudly, so that the isolation of the ticking 
sound was not so satisfactory as in the two previous cases. Still it 
was heard, and when the motions of the disc were kept in one direc- 
tion its loudness did not grow with the extent of the motion. With 
a fine coil and a water cell the ticks were distinct enough ; but the 
mechanical displacement was too small to yield the required com- 
parison. The impossibility of stopping this ticking was illustrated 
in the following way : — A ferrotype plate was held tightly between 
two thin pieces of plate glass, the space between being filled up 
with sealing wax so that the whole was a solid mass of glass and 
wax. This was brought near a core excited by a water cell, when 
the sound was loudly rendered. Another illustration to the same 
effect was that of cementing by sealing wax the ferrotype plate of a 
telephone to a disc of thick microscopic glass, and putting this in 
the telephone with the glass side to the ear or mouth. Its articulate 
functions, though much impaired, still continued. 
Lastly, to test whether the tick in a coil was due to electric con- 
duction, I screwed a pin into the core of the telephone so as to act as 
a prolongation of the core ; round this I placed a coil of fine wire, 
to which the string of a paper telephone was attached. There was 
no ticking heard so long as the circuit of the coil was broken; but 
the moment it was closed the ticking began. The coil was, of 
course, clear of the core. At the same time, however, there was 
mechanical action between the coil and core, illustrating the dif- 
ficulty in such cases of determining by direct observation whether 
the single mechanical pull may not also make itself heard. 
In conclusion, I would say, by way of summing up the evidence 
of this paper, that at the sending station the evidence of molecular 
action, though suggestive, is by no means conclusive ; while at the 
receiving station the existence of molecular as well as mechanical 
