In a paper published in the Transactions of this Society for Session 1877–78, I described an experiment which showed, that if a moderately strong current, such as that from four or five Bunsen cells, be led through two jam-pots filled with fragments of carbon, and if any sound be uttered strongly in the one jampot it will be reproduced distinctly, although faintly, in the other. In this experiment it has been found that the fragments of carbon may be replaced by any kind of loose contact, such as microphones, or a handful of screw-nails put into each jam-pot, or vibrating springs beating against metallic stops, or nails laid across each other in log-hut fashion, and that in each case an effect similar in kind, although it may be differing greatly in degree, is produced. Hence it may be almost laid down as a general experimental result, that if an electric circuit conveying a tolerably strong current contain two places of loose contact, A and B, and if any sound be produced loud enough at A a similar sound will be heard proceeding from B.