HOROLOGY. 



159 



1 ' r . - 



Mo'* mb^ 



Ur peiulu- 



lij ; .' 



PLATE 



. IL 

 Fig 9. 



*a t. 



F .t : 



Ife 3. 



>. 



r* . 



>,. 0. 



u. 7. 



bed wires. To complete the correction, a second pair 

 of wire* of the same diameter as the fanner, anil occu- 

 pying a po-auoi ingiea to them, act downwards, 

 little below the) exterior tube, having also 

 passed through tin- interior one without touching either, 

 wer ends of these wires are fastened to a short cy. 

 lindrical piece of brass, of the same diameter aa the 

 nor tube, to which the bob is suspended by its centre. 

 Fig is a full size section of the rod, in which 

 the three concentric circle* are designed to irfiismiit the 

 two tubes ; and the rectangular position of the two pair of 

 wires round the middle one, are shewn by the five small 



War ft Pendulum. 



Compcnsa 



lion 

 Pendulums. 



ble, which mast hare occurred to me, unless, indeed, 

 I had been impelled on the same idea, by the difficul- 

 ty of contriving the five wires to act all in a row, with 

 nsMsnl freedom and in so small a space. Fig. <). No. S. 

 explains the part which close* the upper end of tle in- 

 terior tube: the two small circles are the two wire* 

 which drpend from it, and the three Urge circles shew 

 the holes in it, through which the middle and other 

 pair of wire* pass. 



Fig. 9. No. *. isdecijfii im the part which 



tops up th- bottom of th il>e; the smalt circle 



in the centre i< where the middle wire is tasusttd to 

 it ; the others the holes for the other four wires to pass 

 through. Fig. < ' ;> the psot which closes the up- 

 per end ofthe external tube; the large cirde in the centre 

 M the place wl. 

 of the middle wire 

 denote the fastening 



- I. 



-far the upper part 

 ml the two small lirclM 

 the wire of the last expansion. 



represent* the bottom of the e tenor tube, 

 h the small circles ah* 

 the wires of the second expansion, and the 

 the hntr* for the <*lier pair of wire* to paw through, 

 ndnoml piece of brass, which shews 

 OAF iH* lower end* of tlSr wire* of th#* lf*t 

 fastened to it. and the hn'r m .! 



i pinned to the centre of the boh. 

 of the upper end* of the t<> pair of wires is done by 

 screwing them into the piece* which stop up the ends 

 of the tubes; but at the lower end* they are all fixed. 

 I have only to add to this 

 in Fig. 9. liave 

 which the fellow 



pair would 'be equally stretched, although 

 they were not enctlv of the 



In the apparatus thiu 



be stretched by the weight of the whole ; the 

 tube will support at iu top the wh 



The rod of this pendulum con-i.-t> of two flat bars of -Want's 

 steel, and one of zinc, connected together by three screws, pendulum, 

 as shewn in Plate CCC V 1 1. Fig. 1 0. No. '2. which is a side p tATE 

 view of the pendulum rod when the bars are together; .rvil. 

 " AA, li," says Mr Ward, " are two flat rods or bars of Kig. 10. 

 iron about an eighth of an inch thick ; tit is a bar of zinc No. - ' 

 interposed between them, and i.* nearly a quarter of an 

 inch thick. The comers of the iron bars are bevelled 

 off, that they may. meet with less resistance from th<: air; 

 and it likewise gives them a much lighter appearance. 

 These bars are kept together by three screws /,/,/, whu-li 

 pew through oblong holes iu A A and k k, and screw into 

 i i. The bar A A is connected to the one k k by the screw 

 m ; which is called the adjusting screw. This screw is 

 tapped into A A, and passes barely through k k ; but 

 that part of the screw which enters k k has its threads 

 turtwxloff. The bar i i has a shoulder ;it iu upper ciul, 

 turned at right angles, and bears at the top of the zinc 

 bar k k, and it supported by it. It is necessary to have 

 several holes for the screw m, in order to adjust the 

 compensation. No. 3, 4, 5, are a side view of each bar 

 separately. No. 6. shews the flat side of the zinc bar. 

 Fig. 10. No. 1. is a front view of the pendulum rod Fij. 10. 

 when screwed together. The letters have the same re. No. 1. 



to the* different figures." 



The front steel bar being lengthened by heat, and Method of 

 having iu itmnmm downwards, will carry along with epmpenss- 

 it the sine bar, whose lower end is supported by a uoa * 

 screw in the front bar ; the sine bar in this case will 

 have its expansion upwards, and carry up the back steel 

 bar, whose upper end reels by msaas of a knee on the 

 upper end of the sine bar The pendulum ball hangs 

 to the lower part of the back steel bar which has its 

 expansion downwards ; but the two expansions down- 

 wards of the steel bars, are compensated by the upward 

 expansion of the line bar. 



Mr Ward's pendulum must be allowed to be a very 

 " one, as it possesses the advantage of permitting 

 saaipn to be readily and easily altered. The 

 which ha* bom given of it. m the Transae* 



I 



description, that the pieces represented in 

 each jointed motto*. by means of whi 

 wire* of CM* air would be euall stretc 



Uons of the Society for the EtMouragrment of Arts, &r. 

 for the year I8O7, and in the pamphlet wind, Mr \\.-.r-.'. 



the second pair of wim will 

 except the middle wire and- inter* 



tchl l.v all 



the exterior 



Btandford in 180*, contain sufficient de 

 tails to enabk- any common clookmaker to copy it. \\ e 

 have only to add, that there should be spare screw, for 

 shifting the pscnpensotinn ; and that the screws con- 

 necting the two steel bars and the sine one should 

 mi any account be moved. It will be found of 

 1 to have a spare screw, which may Be 



tube say ports at its top the weight of the 



of wires and the bob, and the second pair of 



eH*lsid by the weight of the bob only. 



The first pendulum whirh I made of the 

 kind, had only three sterl wires, and one tube above 

 the hob; that it, two expansions down and one up; 

 and the quentr ne of bras* falls short to cor* 



rect two of steel, was compensated for, by extending 

 those branch** of the rod below- the bob. and bringing 

 pan external tube to which the bob was afl&sd. 

 There i* an awkwardness in this construction, owing to 

 the rod reaching about 1 J inches below tor lower edge 

 of the bob. otherwise it is not inferior to the one first 



put into that place which is tuppoecd requisite to cor* 

 rect the compensation ; and then release the one 



to be, where the compensation is thought to be 



are too much or too little. Our experience with it soon led 

 us to this contrivance. Having made one of theie pen- 

 dulums, we hall now give an account of it* <liinrnin, 

 &c. The distance from the upper part of the pendu- 

 lum spring to the centre of the ball, is 40.75 inches ; 

 and to the lower end of the front steel bar, 2 feet 1 1.5 

 inches. From the upper end of the zinc bar, where 

 the back bar of steai rests or hangs on, to the centre 

 of the ball, it is 3 feet 6.25 inches. The steel ban are 

 forged front cast steel, and annealed ; their breadth i 

 throe quarters of an inch, ami their trm-knvM about one- 

 of an in- ,ength of the zinc bar i 2.B 



i ; and it* thickneu a little more thin two-tenthi 



