At the top I always got sound, but at the side I got no sound, although the mercury was shaking. I then tried to see how feeble a current was audible in the telephone. An assistant tapped the tube while I stood out of the way, and where I could not see. I got him to tap it gentler and gentler, and could hear the most feeble tap. A pellet of paper was next dropped from various heights down to an inch, and each tap was perfectly audible in the telephone. I tried many methods, and one, purely accidentally chosen, was a piece of glass tube which I had drawn out into a tube about 2 mm. diameter, and then nearly closed the end of it. I have that tube here, and you will see what an ill-shapen and ugly-looking tube it is, but it is one of the best tubes I ever got; and finally, I found that small bits of thermometer tube, which were simply closed at their ends with a blow-pipe, gave very good results, and I was able to make them useful for various purposes. I then tried mounting a tube on the end of a speaking-trumpet and speaking to the mercury, but got no effect. In every place where I attached the glass tube itself to a sounding-board I got a very accurate reproduction. I put one on a piece of ferrotype plate, and that gave really the best result I ever got. The tube was fastened with sealing-wax, and with it I got excellent speech heard in a Bell receiver. I tried putting in a large number of these tubes, all in quantity, on the bottom of a ferrotype plate, but with no advantage. I have not yet tried putting them in series, one behind the other, so as to increase the electro-motive force, but I think that probably would be an improvement; of course it would require many vessels of acidulated water to dip into. The most distinct articulate speech was obtained from an ordinary ferrotype telephone plate, secured at the edges, and one of the glass tubes you see here attached to it. * * * * * MUNRO'S TELEPHONIC EXPERIMENTS. Mr. J. Munro, whose name is well known not only as a very clear writer upon electrical subjects, but as an original investigator, has recently, with the assistance of Mr. Benjamin Warwick, been conducting a most interesting experimental investigation of the action of the microphone as a telephonic transmitter, with the result of proving that metals may advantageously be employed in the place of carbon in a transmitting instrument, a practical development of one of the very earliest of Professor Hughes' microphones. The fact that metallic electrodes can practically be employed in microphonic transmitters has been denied of late with so much assurance and in such high quarters, that Mr. Munro's successful applications of that portion of Professor Hughes' discovery possess an especial interest, and must to a considerable extent affect the aspect of litigation in future contests in which the discovery of the microphone and the invention of the carbon transmitter are vital points at issue.