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Proceedings of the Royal Society 
The author then proceeded to offer some suggestions as to how 
this alphabet could be applied in the respective cases of signalling 
by means of the heliograph, the light of a lighthouse, steam-whistles, 
flags, and touch ; and advocated the opinion first brought forward 
by Dr J. A. Eussell in a paper read before the Eoyal Scottish 
Society of Arts in 1875, that signalling should be taught in the 
primary schools. 
6. Note on the Wire Microphone. By E. M. Ferguson, Ph.D. 
At our last meeting Professor Chrystal showed us that a fine 
platinum wire attached to a stretched disc of skin could act as an 
electric telephone receiver for the sounds of a violin. The wire 
was included in a galvanic circuit, and the variations of current were 
made by a microphone attached to the violin. The account he gave 
of this interesting experiment was that the receiving wire became 
extended by the heat of the current either as it was established or 
suddenly increased by the microphone, and correspondingly shortened 
on the current ceasing. These extensions and contractions were ren- 
dered audible by the disc. A similar demonstration with a like 
commentary was made by Mr Preece to the Eoyal Society of 
London, an account of which was published in “ Nature ” (June 10). 
Mr Preece got his wires to speak. At the first May meeting of this 
Society in 1878 I discussed the subject of the sounds emitted by fine 
wires, giving passage to intermittent currents. I found that the ordin- 
ary thread telephone gave us an easy means of hearing these sounds 
in non-magnetic metals. De la Eive had heard them in 1845, but 
since his time no one had been able to hear them, and they were 
almost looked on as apocryphal. I attached the thread of the skin 
or paper telephone transversely to the sounding wire, and not directly, 
as Professor Chrystal has done, for the simple reason that I found 
that the transverse method gave equally good results with very much 
less trouble. The cause in both cases seemed to me the same, viz., 
an internal molecular click which marked the setting in and stoppage 
of the current. In the kindly reference that Professor Chrystal 
made to my communication he considered it strange that his simple 
explanation should have been overlooked, that the sounds should be 
set down as having conditions the same as those of heat and yet the 
