188 THE MICROPHONE, ETC. 



of a polished box, about Sin. by 4in. by lin., •without a bottom board, 

 on the top of this a plate of zinc, 4in. by 2Jin., is screwed, this forming 

 the bottom element ; then above this is a plate of carbon of equal dimen- 

 sions. To one end of this plate an upright turned piece of wood, lin. long, 

 is either screwed or glued, and on the top of this a second plate of carbon, 

 2in. by IJin., is screwed. This plate has a binding screw connected with 

 it, and is connected to the lower plate by means of a thin rod of carbon, 

 IJin. long, pointed at the bottom end. Having the instrument finished, 

 all that is necessary is to moisten a pad of blotting paper with a solution 

 of sulphuric acid and bichromate of potash, in the proportion of one each 

 acid and bichromate and ten of water. Place the pad between the 

 carbon and zinc plates, and the instrument will detect the most minute 

 BOimds. For minute sounds the carbon rod should be nearly upright, and 

 for speech should be inclined as much as possible. The Telephone is to 

 be used in circuit, but this may be dispensed with by using a few electro- 

 magnets, made of Jin. iron and bent into the form of a triangle, so that 

 the poles will nearly touch each other. Four of such magnets make a 

 very good receiver. Mr. Blyth has obtained a receiver consisting merely 

 of a box of cinders, with a plate of tin at each end ; but although I 

 have repeated his experiments I have failed to obtain favourable results. 

 A simple form of receiver wiU be obtained in a few weeks, and will at 

 once supersede the Telephone. 



The Magnophone is an addition to the Telephone, by W. L. Scott, 

 and consists in the application of small particles of iron on the back 

 of an ordinai-y Telephone plate, (the plate itself being in the circuit from 

 a series of Daniell's or other cells.) and in the use, as transmitters, of the 

 particles of either iron, silver, gold, or platinum in a state of minute sub- 

 division, or if pieces of asbestos, pumice, or otherbodiosbe saturated with 

 (e. (J.) mercui-y, these phonophoric tablets may be placed in the circuit 

 with pointed ends touching each other, and will then transmit sounds in a 

 similar manner to the Microphone. In fact, the Magnophone resembles 

 the Microphone in so many details that it ought rather to be called 

 a Microphone. 



The Phonoscope is a very beautiful adaptation to an induction 

 coil and rotating vacuum tube. This may be done in the following 

 manner : — At the end of a conical tube a thin membrane is stretched, 

 and behind it a thin plate of platinum, about one-eighth of an inch wide, 

 is attached in a bowed form ; immediately behind this strip of platinum 

 a third point of platinum is fixed into a brass spi'ing. The instrument is 

 a simple form of contact breaker, and contact is made by speaking into 

 the conical tube. Supposing now the tube to be revolving, and the two 

 terminals from secondary of induction coil tobo connected to the two jiicccs 

 of platinum, it is evident that by speaking into the conical tube contact 

 is made and broken m proportion to the period of vibration of the 

 stretched membrane, and the tube will be illuminated when contact 

 is made, and will thus reveal the peculiar condensations, &c., of a 

 sonorous wave. This simple though beautiful adaptation to the 

 induction coil was exhibited by Mr. H. Edmonds, jun., at the conver- 

 sazione of the Institution of Civil Engineers. 



The Phoneidoscopo is simply a tube bent at right angles, and 

 having an orifice, which may bo of any form, covered with a thin film 

 of soap. The film should ap])car coloured, and then, by speaking into 

 the tube, or sounding a tuning foi-k, the coloui-s arrange themselves in a 

 manner very similar to the sand in Chladni's figux'es. The experiment 

 is an instructive one. 



