iSyi.] Electricity. 429 



as may be desired. The driving-clock has, like an ordinary clock, a weight, 

 multiplying wheels, escapement, and a pendulum. For the ordinary pendulum- 

 bob is substituted hollow coils of insulated wire, oscillating over the poles of 

 two compound permanent magnets. An ele&ric current is produced at each 

 oscillation of the pendulum, which current is in one direction as the coil passes 

 from left to right, and in the opposite direction when it proceeds from right to 

 left. These alternately inverted currents are transmitted by conducting wires 

 to the clocks in circuit, in which the escapements usually employed in 

 telegraphic clocks are dispensed with, and the motion of the hands rendered 

 perfectly continuous. The currents proceeding from the driving-clock are 

 caused to pass through a horizontal coil of wire similar to a galvanometer-coil, 

 in the centre of, and above and below which, is an astatic series of magnetised 

 needles fixed on the same arbor, carrying a pinion in connection with the train 

 of wheels communicating its motion to the hands. The needles are propelled 

 for half a revolution by the current which is produced while the pendulum of 

 the driving-clock is moving from right to left, and another half revolution 

 while the pendulum passes from left to right, thus describing a whole revolu- 

 tion in one second, if" half a second is required for each beat of the pendulum. 

 The time when the needles after each half revolution arrive at a position at 

 right angles with the wire of the coil, corresponds exactly with the moment 

 when the pendulum of the driving-clock has arrived at its greatest defledion 

 from the perpendicular. In all former telegraph clocks the current has had to 

 overcome the vis inertia of the magnetised needles of the secondary clocks, 

 thus entailing a great loss of power. But in this clock the currents are aided 

 by the momenta of the needles, so that extremely weak currents arriving at 

 the proper period are sufficient to impart motion to the train of wheels. Thus 

 the needles are aided in their rotation much in the same manner that the 

 oscillations of a heavy pendulum can be maintained by well-timed puffs of 

 breath. The driving-clock can be regulated by a standard clock at any 

 distance, it being understood that the regulator possesses one of the usual 

 contrivances for the momentary completion of a voltaic circuit, or, if in 

 proximity to the driving-clock, that a mechanical connection may be esta- 

 blished. The regulating is effeded by a series of very simple mechanisms, by 

 which the pendulum of the driving-clock is made to shorten or lengthen itself 

 automatically, as the clock has lost or gained. The advantages of employing 

 magneto- instead of voltaic-eledricity as the maintaining power of the 

 secondary clocks are obvious. In every case where the source of power is a 

 voltaic-battery, there must necessarily be established a certain number of 

 contacts, and at each of these interruptions of the circuit a spark, no matter 

 how minute, passes between the metallic points. This spark is nothing more 

 nor less than a piece of the metal in a state of incandescence, and the result of 

 this rapid oxidation of the points is the stoppage of the clock in a few weeks. 

 By employing magneto-eledricity, Sir C. Wheatstone has obtained the inver- 

 sion of" the current in a closed circuit, and consequently avoided the chief 

 cause of failure hitherto. Moreover, the driving-clock can be made to keep 

 time to any degree of nicety, independently of a regulator. 



Another invention of Sir Charles Wheatstone is a magneto-electric counter 

 for registering the number of revolutions or oscillations of any machinery, 

 or the number of visitors to a public building, &c. The instrument consists 

 of a permanent magnet, with soft iron prolongations, on which are wound 

 coils of insulated wire; the currents being induced by the removal and 

 attraction of an armature in connection with the machinery or door whose 

 movements are to be registered. These currents are conveyed to the 

 register, where they ad upon suitable electro-magnets, causing the defledion 

 of a magnetised needle. This defledion is continued by a train of wheels to an 

 index-hand, which points successively to the figures on a dial in the usual 

 manner. The register can thus be placed at any distance from the motor- 

 magnets, out of reach of any ill-disposed person. The door, if the counter be 

 so attached, remaining open, the index of the register points to a space inter- 

 mediate to the two figures, so that the person in charge of the machine can at 



