190 ON PROFESSOR BELL S ARTICULATING TELEPHONE. 



front of an electro-magnet, producing alterations in the intensity 

 of the electrical current, which might be conveyed to a similar 

 electro-magnet, membrane, and piece of iron, at a distant point 

 causing audible vibrations there. Here you will see was the 

 germ of the discovery of the Articulating Telephone, but the first 

 results were unsatisfactory and discouraging. In the earlier forms 

 the transmitting and receiving instruments were of different con- 

 struction. It was soon found that articulation became more 

 distinct as the size of the iron diaphragm glued to the vibrating 

 membrane was increased, and finally the latter was discarded 

 altogether, and an iron plate used instead. It was then found, as 

 had been long anticipated, that the effects were equally audible 

 when a rod of magnetised steel was substituted for the iron core 

 of the permanent magnet ; — and thus was reached the present 

 form of the instrument which I have had the honour of bringing 

 under your notice this evening. 



WM. LANT CARPENTER. 



POSTSCRIPT. 



Since the above paper was read, a Lecture on the Telephone 

 delivered by Professor Bell to the Society of Telegraph Engineers, 

 on Oct. 31st, 1877, has been published by E. & F. N. Spon, 46, 

 Charing Cross. In this will be found fuller details upon many of 

 the points briefly touched upon in the above paper. In particular, the 

 researches of Helmholtz are dwelt upon, and the attempts of 

 Professor Bell to apply these to multiple telegraphy, increasing 

 many-fold the carrying capacity of a single telegraph wire. In 

 this curious arrangement, several pairs of tuning-forks, or steel 

 reeds, were employed — each pair vibrated to a different note — and 

 one of each pair was placed at each end of the circuit. As, at the 

 receiving end, each instrument only answered to its own pair at 

 the transmitting end, as many currents {i.e., sets of telegraphic 

 signals) could be sent along one wire simultaneously as there 



