A'ov. 21, 1878] 



NATURE 



55 



Regent's Park, will, I think, be satisfied that they may 

 again be so, and that in temper, docility, and working 

 power, they would be equal, if not superior, to the 

 Indian elephant. 



Through the medium of the columns of Nature, 

 perhaps an impetus may be given to a matter that is 

 certainly worthy of consideration, and may elicit further 

 remarks from some of the Indian Keddah officers, who 

 are practically experienced in the mode of dealing with 

 elephants. It is, at aU events, worthy of Sir Bartle 

 Frere's consideration. J. Fayrer 



SYNCHRONISED CLOCKS 



RAILWAYS, among many other services which they 

 have rendered, have made us more particular about 

 keeping our watches and clocks in accordance with some 

 common standard of time, and during the past few years 

 various systems have been tried for the distribution of a 

 standard time from a common centre — in this country 

 Greenwich Observatory. For purposes of public life it 

 is more important to have aU the public and even private 

 time-pieces of a country set according to one standard, 

 than that they should show the correct local time. The 

 latter can easily be ascertained by any one who desires 

 it, if he can be sure of knowing the exact Greenwich 

 time. Cf all the systems that have been tried for 

 ordinary public use, that recently organised by Messrs. 

 Barraud and Lund, of Comhill, seems to us to answer 

 all the requisite conditions. We had the pleasure the 

 other day of inspecting the arrangements made by 

 Messrs. Barraud and Lund for the distribution of Green- 

 wich time from Cornhill as a centre, and we are bound 

 to say that the perseverance and ingenuity displayed 

 deserve success, and we believe that wonderful success 

 has been obtained. Messrs. Barraud and Lund have 

 spared no pains and no expense to perfect their system, 

 which, as a practical and widely useful application of 

 science, is full of instruction. 



Any system for the public service of time-signals by 

 synchronising currents which lays claim to approximate 

 perfection, natvu-ally divides itself into three distinct 

 departments ; i. The maintenance of a standard time- 

 keeper at absolutely correct Greenwich mean time ; 2. 

 The distribution of the time at hourly intervals with the 

 needful apparatus for testing the woik done ; and last but 

 not^least, the particular means adopted to enable the time 

 currents to control or set the various clocks in circuit to 

 true time. As to the standard adopted by Messrs. 

 Barraud and Lund, and which is in direct communication 

 with Greenwich, this is a mercurial regulator of the very 

 best construction with a Graham dead-beat escapement, 

 having the contact springs for the time-current between 

 the dial and upper plate, the dial being pierced so as to 

 allow free access to all parts of this mechanism without 

 otherwise stopping or interfering with the regulator. 

 However excellent such a time-keeper may be some error 

 V, ill always exist ; it will have a daily rate however small, 

 and it becomes important that this errorshould be corrected 

 at least once a-day. In order that this may be effected 

 without actually using any physical connection, Messrs. 

 Barraud and Lund have adopted the following method : — 

 A permanent bar-magnet about 6 inches long, is secured 

 to the pendulum-rod, so as to vibrate about ^\ of an inch 

 from a resistance-coil fastened to the case by a projecting 

 bracket ; a current of electricity passing through this 

 coil, accelerates or retards the vibrations of the pendulum 

 according as the current sent is positive or negative, and 

 the power of the current is adjusted to give one second of 

 influence for one hour of duration. The wires of this 

 adjusting current are connected with a commutator, a 

 small instrument about two inches by three-and-a-half, 

 'having three holes— that in which, a plug is normally 

 I placed when no effect is required to be produced, a 



second marked "fast," and a third " slow," for the recep- 

 tion of the plug, according as the standard requires to be 

 accelerated or retarded. In order to secure the con- 

 tinuance of the current for a period neither longer nor 

 shorter than will produce the desired result, a small 

 ordinary clock is interposed between the commutator and 



Fig. I. 



the standard clock. This clock answers a double pur- 

 pose ; it has no hour hand, but only a minute hand, 

 which stands normally at twelve, in which position the 

 clock is "stopped," and no current can pass through to 

 the resistance coiL The plug having first been placed in 

 the " fast" or " slow" hole, as occasion may require, the 



Fig. 2. 



clock is set back, say one hali'-hour for half a second 

 error of the standard. The mere fact of setting back this 

 hand, starts the small clock and closes the current at the 

 same moment, continuing to keep a closed current, till 

 the hand returns to 12, Avhen it again breaks contact and 

 stops itself. It wUl thus be seen that one operation alone 



Fig. 3. 



is requ'red to set the standard, the whole action auto- 

 matically ceasing the moment the standard is '•' to time." 

 The "distributor" is, in fact, a conipound "relay" 

 for twelve circuits, it having been determined to use inde- ' 

 pendent batteries for each line wire in preference to split 

 currents, as used in the chronopher at St. Martin's-le- 



