HOROLOGY. 



163 



dulum which was at OM of the clocks, was of Ward's 

 kind. On its being taken away, a gridiron one was 

 put in its place ; but with this, which was longer than 

 Ward's, the clocks could never be brought to the 

 tame time as before. Their arcs of vibration continu- 

 ally rarfed, and no satisfactory going could be obtain- 

 ed from them, althoueh we were well aware that they 

 were competent to have given a rery different perform- 

 ance. The gridiron pendulum clock waft one of the best 

 poiuble in it execution, ami had one of the best recoil- 

 ing 'scapements we have ever seen or nude. The clock 

 was taken from its case, to have a 'scapement of a diffe- 

 rent kind put in. In the meanwhile, the pendulum being 

 tefl hanging in iti place, was observed to be in motion, 

 which was at first imputed to some shaking of the house. 

 On being stopped, it got again into motion, and upon 

 observing it narrowly, it was found not to be in such 

 a direct ion * any shaking of the house could produce, 

 twinging quite in time with the pendulum of the going 

 clock, the two pendulums mutually receding and ap- 

 proaching each other. The cure was instantly obvious ; 

 and after the upper plank was sawed through between 

 the clocks, the pendulum became in a Tittle while dead 

 and still. The arc in which it vibrated was about twelve 

 minutes of a degree on each *tde of the point of ret, 

 which was nearly about the greatest extent of variation 

 in the arcs of the two pendulums. It would be impos- 

 sible to make two clock* go closely together, in any 

 other situation than the one which has lieeii mentioned. 

 After the pi ink was cut through, the going clock 

 was observed to be losing nearly at the rate of a second 

 and a half a day ; and if the clock which kept so long 

 in unison with it had been tried utwler the same cir- 

 cumstances, it is probable that the rate would hare been 

 found to be fat. The rate they had for a period of 

 grit or nine month* or more, when they went close 

 together, did not exceed two-tenth* of a second fast a 

 day, and this may have been a mean of the natoral rate 

 of each pendulum, if it may be so expressed ; that i, 

 suppose one dock was going rlow 1.5 second per day, 

 the other fast 1 .7 second, there will be two- tenth* of a 

 second left for the acceleration of both, which seem* to 

 be the only way of explaining this phenomenon. 



\p. xnr. 



O Turret 



We hare frequently *een turret clock* put up in 



places where no advantage was taken of the length of 



laM for the weight*, mhich either did not descend 



t, or if they did, the ropes hd 



a second rewinding; as it were, on the barrel. I 



ley, who wa certainly a mwi of genius, and whose tur- 



ret clocks were perhaps unequalled in regard to their ex- 



ecution, though defective from no advantage l>eing ta- 



ken of the fall, made them all with barrel* of a small 



diameter, and of rach a length as to admit ahnoat any 



numl*er of turn*, o that they could be plarrd in .iny 



ier with propriety or not We shall 



therefore lay down *urh ru!r, tha* <Vermayfit 



up a turret dock suited to any given (all for the weMaU 



ov that the height of fall for the weight* is 



t, and that the clocfc is required to go eight day* 



without I ! with a single line to the 



-ithnopn i hang on. 



We may allow 1 2 inches for what the weight will take. 



Thb reduces the length of faH to *4 feet ; allowing 16 



turns of the barrel to give 8 days going, and dividing the 

 '.?+ feet of fall by 1H, we shall have during the length of 

 the rope 18 inches for one turn of the barrel. To find the 

 diameter of the barrel, we say, as 355 for the circum- 

 ference is to a diameter of 113, so is the circumference 

 18 inches of the barrel to its required diameter, whicli 

 will be found to be 5.73 inches nearly. But this dia- 

 meter would be too large, since the diameter of the 

 rope must be taken into account ; for the true diiinu'- 

 ter, or that which is necessary to run out the fall, must 

 be taken at the centre of the rope when wound round 

 the barrel. Allowing the diameter of the rope to be 

 half an inch, then taking this from 5.73 inches, we 

 shall have for the proper diameter of the bnrrel 5.2S 

 inches. Having now obtained the diameter of tht 

 barrel, its length between the ends may easily be found. 

 Sixteen turns of the barrel, the number wanted to pro- 

 duce eight days going, and a rope of half an inch in di- 

 ameter, will require eijjht inches : but a^ the coils of the 

 rope cannot lie quite close to each other, we may allow, 

 for freedom, one inch and a quarter, consequently if 

 the barrel is made 9.25 inches in length between the 

 ends, it will be sufficiently long. For the striking 

 part, a rope of half an inch in diameter will be strong 

 enough, and as one of a considerably smaller diame- 

 ter, even one-half, would suit the going part, the go- 

 ing barrel may be made shorter. If the clock should 

 be made to jro by a double line and pulley, tlicn the 

 diameter of the barrel* will require to be the double of 

 52* inched, or I0.4fi inches. Or if the fall is only 

 13 or If feet, thtti the liarrels of 5.23 inches in diame- 

 ter would do, by means of a pulley. The diameter of 

 the pulley will in part lessen the length of the fall, and 

 in place of 18 mcbe* we may now deduct 16 inches, 

 or so, from the fall, on account of the length taken up 

 by the weight and pulley ; but thi trifling circum- 

 tt'ance require* little accommodation on the part of the 

 Hockmikrr. Taking then the diameter of the barrel 

 at 10. ; in order to ascertain what diamt ter the 



barrel ends and the great wheel ought to have, the rope 

 being half an inch in diameter, t in' this added to the 

 barrel's diameter will make it 11.46 inches, but, for 

 die take of even numbers, let it be taken at 1 1 inche* 

 and a half for the diameter of the plain barrel end ; an 

 additional inch, or I .' 5 inch** in diameter for the bar- 

 rel ratchet end ought to do, unless when the barrel 

 ratchet is pot on the barrel end, and within it- diame- 

 ter, as is sometimes done, in order to have the great 

 wheel of a less diameter than it otherwise would be, 

 when the barrel ratchet end is done in the usual way. 

 The centre of motion of the ratchet end click need not 

 be more distant from the top of the ratchet than half an 

 inch, or at m*t .6 of an inch, and .75 of an inch more 

 than this fbr the bresxhh of the wheel rim, including 

 the teeth. The aemidiameter of the barrel ratchet end 

 is 0.25 mche* ; to thw being added .6 of an inch, and 

 an inch, we shall have for the semidiameter of the 

 great wheel 7.K inches, or it* diameter 15.2 inches. 

 The d : ameter of the great wheel being thus obtained, 

 we may get the circumference by saying, a* 1 13 i* to 

 355, o i* 15.2 to the circumference required, which i* 

 found to be 47.75 inches ; this divided hy 2+0, the 

 double of the number of the teeth proposed to be put 

 into the great wheel of the going part, we have for the 

 breadth of each tooth and each space 0.199 of an inch, 

 or nearly .2 of an inch. It it perhaps advisable to have 

 the space a very small degree leu than what is here 

 given ; the teeth will then be somewhat more than 

 .8 of an inch hi breadth. Taking small temporary sejr- 



Tan 



