Augtist 7, 1879] 



NATURE 



345 



' ELECTRICAL CLOCKS AND CLOCKWORK 



IN the year 1843 an electrical pendulum which forms 

 the basis of nearly all succeeding systems of electrical 

 clockwork, was patented by the late Alexander Bain. 

 (See Fig. i.) 



The bob of the pendulum, c, consists of a coil of insu- 

 lated wire. One end of the wire passes to the axis of the 

 tumbler A T, the other, through the suspension spring s, 

 to the plate Pi. Pi P2 are plates, say of zinc and carbon, 

 and are sunk in the earth to form the battery. From Pj 

 a wire Wg proceeds to N. mm is a horse-shoe magnet. 

 Whilst AT leans against n, a current is passing, and c is 



Fig. I. 



magnetic. C has its - and -}- poles facing the -f- and — 

 poles of the horse-shoe magnet. Consequently the 

 pendulum is driven to the left, but when it reaches a 

 certain point, at topples over, the current ceases, and the 

 pendulum returns. The pendulum now proceeds on its 

 swing to the right, but on approaching the limit of its 

 oscillation, overturns AT again, the current is renewed, 

 and the pendulum again propelled to the left. This action 

 automatically repeats itself. Mr. Bain placed within the 

 circuit of his pendulum any number of electric.il dials. 

 Fig. 2 shows the mechanism of these, c is a coil either 

 in the line of Wj or Wj. When a current passes C becomes 



magnetic, and oscillates between the magnets mm. At 

 every swing of c a tooth, Tj, of the wheel is gathered up 

 by the detent dd. The click, kk, by holding a tooth, 

 T2, prevents the wheel returning whilst D is passing to 

 the right. 



The impulse on Mr. Bain's pendulum varied with the 

 power of his battery, a condition fatal to good time- 

 keeping. In 1849 Mr. Shepherd patented a system in 

 which the current was employed to lift a slight weight or 



Fig. 3. 



spring. The fall of this propelled his'pendulum, and gave 

 an impulse quite independent of any variation in the 

 power of his battery. Fig. 3 shows one of his plans. 



pp is the pendulum, w a weight, mounted on a lever 

 WCA. WCA can move about a centre C, and is at present 

 prevented from turning by the catch ss. When PP 

 swings to the right, the lower screw in PP passes under e 

 (see side view z) and frees wcA. wcA, under the weight 

 of W, propels the pendulum to the left till stopped by a 



Fig. 3. 



banking B, PP moves on and makes contact with T, 

 whereupon a current passes, MiM, become magnetised, 

 and attract ll, the vertical arm of which lifts wcA over 

 the catch S S again. When P p leaves T the current ceases, 

 and LL is carried back to its old position by the action of 

 the spring R. 



Mr. Bain's and Mr. Shepherd's are the leadmg types 

 of electrical clocks properly so called, that is to say, of 

 clocks which keep themselves going by electricity. But it 



