_M. Demoget’s System._--Several other systems of telephones with multiple membranes have been proposed. One of them, planned by M. Demoget, consists in placing before the vibrating disk of the ordinary Bell telephone, separated by the space of a millimètre, one or two similar vibrating disks, taking care to pierce in the centre of the first a circular hole of the same diameter as that of the bar magnet, and to pierce a larger hole in the second membrane. The inventor asserts that the distinctness as well as the intensity of sounds is increased in this way. ‘By this arrangement,’ says M. Demoget, ‘since the vibrating magnetic mass is larger in proportion to the magnet, the electro-motive force of the currents generated is increased, and consequently the vibrations of the disks of the second telephone are more perceptible.’ _Mr. McTighe’s Telephone._--In this telephone, which has several diaphragms, there is a horseshoe magnet, and instead of placing the coils upon the poles, there is a single coil fastened to an iron core, which is inserted between wide polar appendices fitted to the two poles of the magnet. These appendices consist of thin plates, which act as vibrating plates. _Modifications in the arrangement of Telephonic Organs._--We see that the forms given to the Bell telephone are very varied, and this is still more the case with its constituent organs, without, however, producing any remarkable improvements. Mr. Preece observes that little has been gained by varying the size and strength of the magnets, and the best effects have been obtained by using the horseshoe magnets directed by Mr. Bell himself. The telephone was certainly introduced into Europe with the arrangement which is theoretically the best, although Mr. Bell is still occupied in improving it. This is also the opinion of M. Hellesen, who, like Mr. Preece, has made many experiments on this point; but this has not deterred several people from declaring that they have discovered the way of making a telephone speak so as to be audible to an assembly of people. Of the different instruments made with this object, that of M. Righi seems to be the most important. It was lately tried with success at the Académie des Sciences, the Conservatoire des Arts et Métiers, and the Press pavilion of the Exhibition. [Illustration: FIG. 37.] The receiver is only a Bell telephone of large size, with a diaphragm of parchment L L (fig. 37), in the centre of which there is a sheet-iron disk F. This membrane is stretched on a large funnel E, which is fixed on a box C C, containing the electro-magnetic coil B: and the magnet N S, much larger than in the ordinary instruments, issues from the box, and serves as its support. [Illustration: FIG. 38.]