HOROLOGY. 



161 



ith a 

 wooJcand. 



FtATC 



II. 



V-.f 11. 



ITfeft* tber in a great degree, tlie very defect which Mr Ludlam 

 ^^vatt wanted to avoid. The Literal coming and going of the 

 pendulum rod by heat and moisture, causes the screws 

 """"" ** to come and go from the crutch, sometimes to clip it 

 hard, and at other times to allow it to have more free- 

 dom between the ends or points of the screws than is 

 proper. Finding that it had a strong tendency to gy- 

 ratory motion when tlie clock was set agoing, (which 

 however diminislied some time after,) arising from the 

 mass of the ball being carried out from the centre to- 

 wards the edge, and from a thick rod passing through the 

 centre, we thought of the following pendulum, which 

 was afterwards put in execution, where the greater 

 part of the mass of the ball is kept at the centre, and 

 where the least quantity possible is towards the edge. 

 Mr Rti.i', A drawing of this pendulum, is given in PlateCCCVlI. 

 Fig. 1 1 . No. I . and 2. The ball is of a lenticular form, 

 7 inches in diameter, thickness at the centre 3.5 inches, 

 as seen at AA, AA, having a round wooden rod of 

 about .6 of an inch in diameter, or thereabouts. The 

 rod may be either round, flat, rectangular, or ellip- 

 tical. This last is perhaps the best form ; the trans- 

 verse diameter being 1.5 inch, and the conjugate 0.5 

 of an inch. aa. aa, No. 1. are two small round steel 

 wire*, whose diameter is leas than .2 of an inch, or 

 eay .175 of an inch, the length from pin to pin about 

 .chea. They might be kept shorter if care were 

 taken to regulate the length of the pendulum by the 

 going of the dock before fixing their length; in 

 which case, they need not project more than .2 of an 

 inch beyond the diameter of the ball. The centres of 

 those wires are one inch apart, each passing through 

 the ball at half an inch from the centre ; o I . o 8, 

 No*. 1. and 2. are two piece* of brass, into wiueh the 

 ends of the steel wire* are fitted and pinned fast, their 

 shape represented in the drawing. In one of them 

 - a socket in which the lower end of the rod is 

 fixed ; and in the lower one A 2, the regulating screw a! 

 peases frxly through: , x are two brasa nerrelled nuts, 

 topped to receive the screw d, which has also a conical 

 nerreUed head fixed on it; the lower end of the screw ser- 

 an index forthe arcs of the pendulum's vibrations. 

 he upper end of the screw, the lower edge of the 

 pendulum ball reeta ; and when moved up or down by 

 the screw, the nuts t, * are fcrewed against the braee 

 piece ft 2, in order to keep all fast. 



The advantage* which this pendulum pnsnem. are 

 very obvious. The whole of the momentum of the ball is 

 so near the centre, that it maintains a very steady mo- 

 tion ; and should an v lengthening orehnrtentngof the rod 

 and steel wire* take pUee. this will in some a* agree bo 

 compensated by the ball. Should they lengthen, the ami 

 eauae will make the centre of the ball get upwards, the 

 meanwhile resting on the end of the regulating 

 . tnd viet irria. A piece of flat braes is fitted and 

 phmed into the up 

 drawing, 

 piece of brass 



wood is taken away, in order that the crutch with its 

 pin may get as near a* may be to the piece of brass. 

 The piece of brass in which the lower end of the pen- 

 dulum spring is. i fitted to the top of the rod, having 

 two puie through it. to make it feat there. The upper 

 and is fixed to a piece of brass, which goes on a steel 

 , having pivots to reM on a cock, and turn freely 

 it, w that the pendulum may take its plumb-line 



o the upper part of the rod C C, as seen in the 



Behind the rectangular hole made in this 



rae* to receive the cratch pin. a art of the 



from drawers, whose sides and bottom were of cedar. Wooden 

 there issued effluvia-, that inspissated the oil at the 

 locks, and thickened it so much, that the locks became 

 of no use till they were taken off and cleaned. 



Pendulum rods have sometimes been made of cedar Pendulum 

 wood, and are objectionable on this account, as the oil rods of te- 

 at the pivot holes of the clock becomes thickened by it. dar ood. 

 Perhaps if pendulum rods of cedar were strongly var- 

 nished, this might deprive the wood of this inspissating 

 quality. 



It is of the utmost importance to have the pendulums Method of 

 of clocks well fixed at the point of their suspension ; tiMn S p*- 

 and the cock to which they are suspended should, at Julums - 

 the same time, be strong and firmly fixed to the wall 

 of the place where the clock stands. This requires 

 to be particularly attended to in turret clocks, and stilt 

 more so in clocks intended for astronomical purposes. 

 These last ought to be placed upon an iron bracket. 

 strongly fixed to as massy a stone pier as can possibly 

 be got into the place where the clock is to stand. \\ i- 

 have had an instance of a pendulum which waa so 

 well fixed up, that there did not appear a possibility of 

 its being made any firmer, or that the motion of the pen- 

 dulum could in the least affect the cock and suspension, 

 yet the arc of its vibration was a little inert i*r<l, after 

 having made considerable exertions to put farther home 

 the screws, Ac. concerned with the fixtures of the cock 

 and the suspension of the pendulum. The arc of vi- 

 bration did not exceed two degrees on each side <>t' tin- 

 point of rest, so that its motion, or centrifugal force, 

 could not be very great at the point of ciupenvion ; yet 

 small as this force was, it is clear that it was sufficiently 

 gnat to affect the cock there, aa this cause made the arc 

 of vibration of lee* extent than when the suspension was 

 afterwards more firmly fixed. We have suspended the * 



when h i.- BO, 



It he* been 

 toi_ xi. 



cabinet- makers, that 



on a strong brasa cock, which was either ri- 

 vetted or screwed to an iron plate. This iron plate was 

 screwed firmly to the wall, the dock case being between 

 the plate and the wall, and sometimes a notch was left 

 in the pillar plate to receive the end of the brass cock, 

 by which means the clock frame and the pendulum sus- 

 pension were made to keep together aa nearly as poa. 

 lible ; and when every thing here was so far adjusted, 

 a strong screw with a square bead was put through the 

 cock, buMBiig it and the pendulum top-piece firmly to- 

 gether. Another way is, to have two brass supports 

 screwed on to a very strong seat board. These sup- 

 ports may be about one inch broad and half an inch 

 thick, and in height about six inches, more or less, ac- 

 | to the height of the bending of the pendulum 

 _ above the sent board. Kach support has a strong 

 and bruad sole, and these soles have a stout steady pin to 

 go into the seat board, which is screwed, from underneath 

 the seat board, by strong iron or steel screw fast to the 

 upper side. The supports at the top incline a little to- 

 wards each other, and a thick and broad piece of plate 

 braaa is ecieweJ to them behind, so as to connect them 

 firmly together. The upper ends of thesupports are made 

 level, and parallel with the soles and seat board. Acruss 

 these ends is made a triangular notch, to receive the pi- 

 vots of apiece of steel, to which the pen lulum i*uspend- 

 ed. By means of these pivoU the pendulum turns, so 

 aa to hang freely in a vertical position . The di-t'incc be- 

 tween the ends of the braaa supports at the top need not 

 be more than two inches, while at the bottom the dis- 

 tance may he four inches, or not quite K> much, tin- in- 

 clination being about ten degrees or so from the per. 

 x 



