It was shown some time ago by Dr Ferguson, and more recently by Professor Chrystal and Mr Preece, that a fine wire attached to a mechanical telephone can act very well as a receiver in a telephonic circuit, provided a make and break, or some form of microphone transmitter, be employed. None of these experimenters, however, have said anything about the action of such a wire as a transmitter. Being struck by the convertibility, in general, of all forms of telephone receivers into transmitters, and vice versa, it occurred to me to try how far this wire telephone, as it has been called, could be made to act as a transmitter to an ordinary Bell telephone as receiver. I was much interested to find that it could act in that capacity wonderfully well, as thereby a new element of some importance is introduced into the discussion of the real cause or causes of the action of the wire telephone whether as receiver or as transmitter.