CHAMBERS'S INFORMATION FOR THE PEOPLE. 



electricity, instead of maintaining the pendulum- 

 motion immediately, draws up a weight which 

 discharges that function, on the principle of the 

 gravity escapement. 



But more important is the device of Mr Jones 

 mentioned above. It consists in making a stan- 

 dard clock of the usual construction to regulate 

 the flow of a galvanic current, and thus control 

 the action of any number of secondary clocks, 

 also of the ordinary construction. The pendu- 

 lums are not intrusted solely to the stimulus of 

 the electricity, but are moved by their own weights, 

 as in ordinary clocks, so that if the electricity 

 ceased to be sent to them, they would go on with- 

 out it. It might be supposed that a confusion of 

 the two forces, electricity and gravity, would 

 ensue ; such, however, is not the case. While the 

 motion of the clock is intrusted to its own weight, 

 the pendulum submits docilely to the controlling 

 action of the electricity; and thus a secondary 

 clock of little value may be invested with all the 

 perfection of the most costly observatory clock. 

 The success of Jones's pendulum has been severely 

 tested in the arrangement employed by Professor 

 Smyth for firing the one o'clock time-gun at Edin- 

 burgh. A clock in the Castle of Edinburgh is 

 made to liberate the trigger of the gun exactly at 

 one o'clock. This clock is regulated on Jones's 

 principle, by a clock at the Observatory on the 

 Calton Hill, nearly a mile distant. The Obser- 

 vatory clock, by means of electricity, sets off a 

 time-ball on a neighbouring monument at the 

 same instant. The fall of the ball, and the flash 

 of the gun, though occasioned each by its own 

 clock, are perfectly simultaneous. 



Miscellaneous Clock-work. 



The applications of clock-work to other pur- 

 poses than that of measuring time are numerous 

 and important In all of them, however, the prin- 

 ciple is the same namely, the indication of space, 

 or, what is equivalent, the indication of time or 

 number by mechanical motion. All our meters, 

 by which the discharge of gases and liquids is 

 now measured, are but combinations of clock- 

 work ; as are also those numerous inventions for 

 registering events connected with atmospheric 

 temperature, rise and fall of barometric pressure, 

 direction and force of wind, vigilance of sentinels, 

 and the like. 



Thus, by a properly constructed anemometer 

 (literally, wind-measurer), not only may the force 

 and direction of the wind be ascertained at any 

 given moment, but the instrument may be made 

 to trace or register the direction from which, and 

 the force with which, the aerial current has swept 

 during every minute of the day all that is neces- 

 sary being, to place under the tracing-pencils a 

 clean sheet of paper every twenty-four hours. A 

 curious time-keeping method of insuring the 

 presence and attention of night-watchmen has 

 been successfully tried. It consists of a clock 

 with pins projecting round the dial, which can 

 only be pushed inwards at a certain interval, 

 when the watchman's presence and attention are 

 required to unlock the case, and do so ; otherwise, 

 his neglect, and the exact quarter of an hour at 

 which he was absent, are shewn by the tell-tale. 



Closely allied to these varieties of clock-work, 

 but evincing a greater degree of scientific skill, 



300 



are the various machines which have from time to 

 time been invented to lessen the drudgery of long 

 and continuous calculation. The most ambitious 

 of those contrivances were those projected by the 

 late Mr Babbage, but none of them, we believe, 

 were so far perfected as to do actual work. The 

 Arithmometer of M. Thomas of Colmar executes 

 all ordinary arithmetical operations, and is in 

 actual use. Opinions, however, are divided as to 

 possible advantages derivable from such machines. 

 In the Journal of the Institute of Actuaries for 

 July 1871, two writers uphold their utility on the 

 ground of actual experience ; another, after point- 

 ing out their drawbacks, and the limits of their 

 use, concludes that ' arithmeticians have not 

 much to expect from the aid of calculating ma- 

 chines. A few tables, otherwise easily made, com- 

 prise the whole extent of our expected benefits.' 



WATCHES. 



Clocks and watches are certainly amongst the 

 most perfect, as, in the civilised world, they are 

 the most indispensable machines ever produced 

 by human ingenuity. ' To become a good watch- 

 maker,' says Berthoud, ' it is necessary to be an 

 arithmetician, in order to find the revolutions of 

 each wheel ; a geometrician, to determine the 

 curve of the teeth ; a mechanician, to find the 

 forces that must be applied ; and an artist, to be 

 able to put into execution the principles and rules 

 which these sciences prescribe. He must know 

 how fluids resist bodies in motion ; the effects of 

 heat and cold on different metals ; and, in addi- 

 tion to these acquirements, he must be endowed 

 by nature with a happy genius.' No one who has 

 not closely attended to the matter, can conceive 

 the difficulty which has been experienced even in 

 dividing circles for the wheels of a watch into the 

 requisite number of rigorously equal parts, and in 

 'pitching' them in, or adjusting them one with 

 another. All the resources of art shewn by Rams- 

 den, Troughton, and other eminent mathematical 

 instrument-makers, have been here called into 

 requisition. And as to the delicacy of touch and 

 adjustment necessary in the mere regulation of the 

 mechanism, after being thus accurately made and 

 'pitched in,' some slight idea may be formed 

 from the fact, which we give in the words of Mr 

 Thomson, that ' a second (a mere pulsation) is 

 divided into four or five parts, marked by the 

 vibrations of a watch-balance, and each of these 

 divisions is frequently required to be lessened an 

 exact 288oth part of its momentary duration !' 



Before entering upon a description of the various 

 parts, we here present the general arrangement of 

 the wheel-work of a common vertical watch the 

 frame-plates being omitted, and the dial being 

 supposed to be turned downwards. B is the 

 barrel or drum, containing the spring which pro- 

 duces the motion. F is the fusee, connected with 



the barrel by the chain c. W is the fusee-wheel, 

 called also the first or great wheel, which turns 

 with the fusee, and works into the pinion D, called 



