SCIENTIFIC SUMMARY. 
431 
has recently been working m London, and has conveyed musical sounds 
between tbe Canterbury Hall and tbe Queen’s Theatre. Mr. Varley’s in- 
vention dates back to 1870, when be patented a method, or rather several 
methods, whereby he could send rapid electrical undulations along an or- 
dinary telegraph line, and reproduce these undulations as audible sounds at 
the other end. A tuning-fork, with one leg longer than the other, and 
having its shank connected with a battery, is caused to vibrate between a 
pair of electro-magnets. The vibrations generate momentary currents in 
the two primaries of an induction-coil, which are also connected with the 
battery. These currents in the primaries induce a succession of alternate 
currents or electric undulations in the secondary coil ; and by means of a 
signalling-key these undulations are caused to alternately charge and dis- 
charge a condenser attached to the line. Hence a series of electric waves 
are caused to traverse the line, in unison with the vibrations of the fork. 
Or instead of the fork, a vibrating reed may be employed. The undulations 
which are thus transmitted are received at the opposite end of the line by 
an apparatus called a cymaphen , of which several different forms are de- 
scribed by the inventor. If the currents pass round a helix containing an 
iron rod, the latter is caused to vibrate ; or if the coil contain a magnetized 
harmonium tongue, this in like manner will vibrate, and in either case 
musical sounds are produced. Again, if the currents circulate through a 
wire helix which encloses a hard-drawn iron or steel wire, stretched over 
bridges on a sounding board, the wire is magnetized whenever a current 
passes through the coil, and is alternately attracted and repelled by a pair 
of electro-magnets, one on each side of the wire ; the vibrating wire then 
emits sounds similar to those of the oscillating tuning-fork at the transmit- 
ting station. Moreover, it is possible to obtain a musical note by the rapid 
charge and discharge of a condenser at the receiving end. In any of these 
ways audible sounds may be obtained, corresponding with the vibrations of 
a tuning-fork or of a reed at the distant end of a telegraphic line. 
During the years 1874, 1875, and 1876, patents for various forms of tele- 
phone were obtained in this country by Mr. Elisha Gray, of Chicago. 
Without entering into the details of the mechanism by which the patentee 
sends a succession of electric impulses along a telegraphic line — as by the 
vibration of a series of tuning-forks of different pitch — it is sufficient to call 
attention to one extraordinary form of his receiving apparatus. This curious 
instrument is sometimes called the “physiological receiver,” for reasons 
which will be obvious on explaining its action. It consists of a small 
cylindrical box of thin wood, with one face of sheet zinc slightly bulged 
out, and having an air-hole in the centre. The box is mounted on a hori- 
zontal axle, by which it can be rapidly rotated in a vertical plane. The 
electric current from the line passes, in most forms of this telephone, to the 
primary wire of an induction coil, and thence to the earth. One end of the 
secondary wire of this coil is connected with the axle of the receiver, and 
thence with the zinc face, while the other end of the wire is held in the 
hands of the operator. With one linger of that hand he presses upon the 
zinc disc, while he rotates the apparatus with the other hand. On the 
passage of an induced current, which is thus forced to pass through the body 
of the operator, who is in the secondary circuit, a distinct musical note is 
