346 



NATURE 



\_Atigust 7, 1879 



is scarcely worth while to use electricity when you can get 

 gravity more cheaply. And do what you will, you can never 

 absolutely rely on getting your current when you want it. 

 For these reasons purely electrical clocks are very seldom 

 used, it being found better to do whatever electrical work 

 is required, by an ordinary clock with galvanic contact 

 apparatus affixed. But though electrical clocks pure and 

 :simple have not made much progress, the system of 

 cor.trolling a quantity of indifferent clocks from one good 

 one has. This principle was invented by Mr. Jones, of 

 •Chester, and Fig. 4 shows it. 



(3) is the pendulum of the controlling clock, and (2) that 

 of a controlled clock ; (i) is a side view of (2). c, the bob 

 of (2) is a hollow coil of insulated wire, and swings over 

 two magnets. Mi Mg, which have their similar poles facing 

 each other. The ends of the wire forming c are carried 

 up the pendulum, pass respectively through s, Sj, and 

 terminate in t, Tj. t, is joined to t, which crowns the 

 pendulum of the controlling clock, and Tj is in connection 

 with both Ni Nj, the contact springs of the same. Both 

 Ni N2 have their respective batteries, Bi B^, but with oppo- 

 site poles towards j ; so that if C is magnetised in one 



'^il Vz 



yr.l m 



Fig. 4 



■direction by one, it will be magnetised in the opposite 

 by the other. 



Suppose (2) has a tendency to lag as compared with (3). 

 When (3) approaches the extremity of its swing, G meets 

 N„ a current passes, c is magnetised and is pulled on 

 smartly. When G leaves Nj, the current ceases. G goes 

 to meet Nj, then c, which is now over Mj, is again mag- 

 netised, but in the reverse direction. Mg being also 

 reversed as regards Mj, c, if behind, is pulled on again. 

 Should (2) be in front of (3) its motion would be checked. 

 A great many clocks can by this method be kept swinging 

 in unison together. 



Mr. Ritchie, of 25, Leith Street, Edinburgh, has 



patented an ingenious modification of the above. He 

 places in the circuit of his controlling clock not other 

 clocks, but pendulums. These he drives in just the same 

 way as Mr. Jones controls his, and each pendulum works 

 a train of wheels which move hands. Mr. Ritchie's are 

 really electrical dials, but they have this great advantage, 

 that should the current fail, as currents are apt to occa- 

 sionally, the momentum of the pendulums is sufficient to 

 keep the dials moving for a short time independently of 

 it. The method by which the pendulums drive the wheel 

 work is interesting (see Fig. 5). 



A and B, the pallets, swing loose, s, the escape wheel, 

 is now being held against a^ a stop on A, by the weight of 



