B IB01 .v. 



HOI OLOOY. 



: I 



, to what may be termed lever-frame, ope side of which is 

 in the cut at y, A, i , the lever frame itwlf it pivoted to the clock- 



ng.it. 



Airy'i mninUiining.powtr Fuccr. 



plate* at A. To the end i the end of the line 1; I, is attached, after 

 jmtrng under a running pulley attached to the weight w. r is an 

 internal ratchet on the first wheel a, acted upon by the long click ui, 

 which baa iu opposite end attached to the lever-frame near its extr- 

 mity i. While the clock a going in the ordinary way, the descent of w 

 cause* that part of the line marked I to turn the barrel in the direction 

 of the arrow, carrying with it the first wheel a, the internal ratchet of 

 which Mip under, without being affected by, the click m. Under 

 these circumstances the action of the weight w (through the line 7), 

 and the resistance of the pinion /, produce a certain pressure on the 

 lever-frame at g ; this causes the end i to assume a determinate 

 position, in which it remains without motion so long as the weight 

 continues to descend, and consequently to draw down the line I. 

 But so soon as, by the operation of winding up the clock, the pressure 

 upon / cosmos to operate, the stress of the weight upon the portion of 

 the line marked k causes the end i of the lever-frame to be depressed, 

 and the click n, which is connected with it, to be thrust against the 

 internal ratchet r with sufficient force to maintain the action of the 

 first-wheel a, which turns as it were in one piece with the lever-frame 

 round the axis k ; thereby producing a pressure upon the pinion / 

 exactly corresponding, if the axis A corresponds with the point at which 

 the strain of the line / is applied to the rope-barrel, to the pressure 

 which is exerted during the ordinary action of the machine. 



There is one turret clock which has acquired much notoriety, on 

 account of its aixe and cost, and of the extraordinary amount of 

 controversy to which it has given rise during the long period of sixteen 

 yean ; namely, the clock for the new Houses of Parliament at West- 

 minster. In 1844 Sir Charles Barry applied to Mr. Vulliamy for 

 plans and estimates for a clock that would strike the hours on a bell 

 of eight to ten tons, chime the quarters upon eight smaller bells, and 

 show the time on four dials of 30 feet diameter each. How it arose 

 that the clock was made by Mr. Dent instead of Mr. Vulliamy : that a 

 non-professional man, Mr. . B. Denison, became intimately mixed up 

 with the subject: that the plans underwent numerous modifie 

 and that it was not till 1869 that the clock was actually fixed in its 

 [dace it would be wearisome to tell. It cannot be said that even now 

 (March, 1860) the clock is really finished, owing to the unfortunate 

 failure of the great bell (for which see BELL). The chief features 

 of the mechanism are as follow. The going part is arranged for 

 winding-up once a week ; but the striking apparatus goes for 

 wren and a half days, to allow for slight delays ; and even a delay 

 of one whole day, though it would stop the striking, would not 

 stop the going, the latter being arranged for eight and a half days. 

 The ponderous weights hang down a shaft 160 feet deep. Scheme* 

 have been proposed for employing both steam power and water 

 power to wind up the clock ; but at present manual |x>wer only it 

 employed, and a most laborious duty it is. The pendulum is 16 

 feet long, and weighs 680 pound* ; it is formed of an exterior iron 

 tube 4 inches in diameter, with a compensating inner tul>c of zinc. 

 It is a two-seconds' pendulum, with a swing or vibrating arc of 14 

 inches; a small weight of only one ounce, placed on a particular 

 part of the apparatus, will alter the rota of the clock one second 

 per day. The hammers of all the bells [1:1:1.1.] arc (or rather, 

 are intended to be) worked by their levers or handles catching 

 against cam* on the edge* of wheels ; the great or hour-bell being 

 worked by eighteen earns on k wheel 37 inches in diameter. On 



the four (ides of the clock-tower are dial rooms, each an apartment 

 of large sise, traversed by mechanism which communicates i 



the clock to the hands. There U at Mechlin a larger clock 

 dial than those at Westminster ; but there is no second example of 

 .1 1 -A with four dials 224 f*et in diameter, and provided with 

 minute hands as well as hour hands. The frame-work of each dial, 

 lean than 4 tons, and including the quarter-hour and 

 minute subdivisions, is of cast iron. Tin- hour figures are 2 feet high 

 and (i feet apart; and the minute marks are 14 inches apart. There 

 is a rrmwil'iirr apparatus, to give a ritiile motion of the long hand 

 every half minute, when the point of the hand makes a sudden leap of 

 7 Inch**. The bauds weigh more than 2 hundredweight the pair ; 

 the minute hand being 1'i feet long and the hour hand 9 feet. In 

 onler that (when all is completed) the indications of the clock may 

 be visible at night, the framework of each dial is fitted iu with 

 op:il or enamelled glass; provision U made for sixty gas jets 1 

 the dial ; and the clock itself will turn on and off the gas, according 

 to the length of night at different seasons of the year. 



Electrical and Illuminated Clock*. So numerous have been the 

 novelties in the clock and watch manufacture within the last few years, 

 that the bare enumeration of the names of inventors would occupy a 

 considerable space. We need only, however, notice electrical and 

 illuminated clocks. 



The hopes once entertained concerning electrical clocks have scarcely 

 been realised. These ingenious machines are not yet largely employed 

 in our great centres of business. There are two kin.N. which 

 may be distinguished aa electrical diab and electrical clock* proper. 

 An electrical dial is a clock-dial, without any body belonging to it. 

 There is a standard clock at some other place, such as the Obser- 

 vatory at Greenwich ; there is an electric wire connecting the 

 standard clock with the index hands of the dial ; and there is 

 apparatus for sending a galvanic current through the wire at certain 

 equidistant intervals of time. The result of this arrangement i 

 the dial-hands make a leap over a small portion of their 

 course, whenever a current passes through the wire ; and the figures 

 marked on the dial give a tune-value to this movement. The interval 

 of the shocks may be a minute, half-minute, or any other amount 

 chosen. It is quite possible to make the hands mark seconds' move- 

 ments, to correspond with the pendulum-beats of a standard-clock ; 

 but in practice it is found better that the long hand should only make 

 hall-minute jumps. An electric clock, in the proper sense of the term, 

 is one that carries its source of power with it, independent of any con- 

 ducting wire from another building. Various modes of effecting 

 this have been devised by Shepherd, Dent, Airy, and others. In 

 the first attempts, electricity was employed to impel the pendulum 

 itself ; but it was afterwards found better to apply the power in raising 

 a small weight, which may then work the pendulum after the manner 

 of a gravity escapement. In Shepherd's Magnetic Striking Clock, the 

 vibrations of the pendulum arte caused by the repeated impulses of a 

 fine spring i the attraction of an electro-magnet being employed solely 

 to relieve the pendulum from the action of the spring during the 

 return or reflex vibration. The hands are moved by separate electro- 

 magnets, the circuit of the wires being completed and broken by the 

 pendulum as it swings. The number to be struck is regulated by a 

 locking-plate divided in the usual way, the hammer being moved by 

 the direct action of an electro-magnet. Electrical clocks or electrical 

 dials are used in astronomical observatories, and by telegraph compa- 

 nies, but very little in other quarters. 



Intimately allied with this subject is the action of Electric Time-bail*. 

 These are contrivances for showing exact time once a day only, and in 

 a manner to be visible throughout a whole district. The interval may 

 be more or less than one whole day ; but this is selected as being most 

 convenient. A large ball is seen to fall at one o'clock in the day ; and 

 this fall may safely be taken, by mariners and others, as a guide for 

 correcting chronometers, watches, and clocks. The time-ball at Green- 

 wich Observatory, and that of the Electric Telegraph station in ih.' 

 Strand, may be taken as familiar examples. The Greenwich ball is a 

 basket of wicker-work, covered on the exterior ; when it descends, a 

 piston plunge* into a tube, compresses the air, and thus, makes a kind 

 of soft cushion which enables the ball to drop without concussion a 

 small hole in the bottom being left for the air to escape gradually. At 

 a few minutes before one o'clock, the ball is wound up by hand to the 

 top of the staff. At one o'clock, to a single second, the standard 

 in the observatory, by means of delicate mochanism, sends a current of 

 electricity which loosens a , trigger and lets the ball sink. The time 

 Kill in the Strand, of later" construction than that at Grecnwi 

 hibit* many improvements in detail. Several others have since been 

 established at the outport*. 



The rendering of clocks visible at night is one of the many im- 

 provements introduced in recent years. The illumination is ett'ocied 

 in many way*. At the Homo Guards in Whitehall, light iR thrown 

 ..u tin- face of a dial from a gas-fiaine hidden behind a parapet. The 

 ii.iual method is to make the dial eit,hrr wholly or chiefly of 

 wnii-.paiiuc glass, and to manage the lighting in the way just noticed 

 concerning the (prospective) arrangements for the W**tminstr olook, 

 Such dialn, however, are not *o conspicuous and convenient during 

 the day a those of ordinary construction ; and it is difficult to 

 n the hands in a well-adjusted condition. A suggestion w 



