IMPROVEMENTS IN CLOCK-ESCAPEMENTS. 429 



requires much smaller weights than when they are laid on the top of the bob. Moreover in 

 long church-clock pendulums the bob is often unapproachable, except by a ladder. 



There was an astronomical clock from Denmark in the Exhibition, which struck a bell 

 at every minute, in order that an observer might look through his telescope without inter- 

 ruption, taking the time from the clock entirely by ear. I never could get hold of any person 

 to shew the inside of it, and therefore I do not know whether there was any provision to 

 prevent the friction of raising the striking work from affecting the pendulum ; and without 

 such a provision it is impossible to make a striking-clock keep very good time. But with a 

 gravity escapement tolerably independent of the force of the train, it may be done very 

 easily ; and I should suppose that the striking at every minute would be a convenient addition 

 to an observatory clock. 



It may save some trouble if I give a few practical directions as to the best mode of 

 arranging the works of a clock with this escapement. 



The scape-wheel should be near the bottom, on account of the length of the arms, so that 

 the seconds' dial and the hour dial will be reversed from their usual places in astronomical 

 clocks. The scape-wheel stands behind the back plate with its back pivot in a cock ; and 

 the front pivot had better be in a cock also for convenience of taking it out. The fly on the 

 scape-wheel arbor is between the plates: a fly about an inch wide, and each arm 1^ in. long, 

 will be large enough. And in order to leave room for the fly, the arbor of the wheel next to 

 the scape-wheel is made short, and one end set in a cock within the front plate of the clock, 

 (with the screw-head outside), and the other (which carries the seconds' hand) goes through the 

 cock which carries the front pivot of the scape-wheel arbor. The lower part of both the 

 plates had better be cut away in the middle, in something like a semicircle, up to the cocks 

 of the scape-wheel, so as to let the escapement be seen from the front. To make the angle y 

 (at which the pendulum changes the arms) = 1° the distance of the centers of the scape-wheel 

 pins from the center of the wheel must be ^th of the length of the arms down to the stops; 



or ^th to make y = 40' or - . 



The pendulum must be made to swing 2° by adjusting the weight of the arms, on which 

 horizontal projecting pieces may be left at first, as shewn in the drawing of the escapement 

 to be cut or filed down afterwards until the arc is reduced to 2°. 



The adjustment for beat is made, as shewn in the drawing of the escapement, by merely 

 bending out the lower ends of the arms below the stops (making them long enough for the 

 purpose) so as to embrace the pendulum. They will not however touch it, and the contact is 

 made by inserting in the pendulum-rod on opposite sides two steel screws with broad heads, 

 a little convex, and with the edges rough so as to turn by hand. The screw on one side must 

 be a little above that on the other, that the screw-holes may be clear of each other ; and the 

 arms should touch the screws just at or a little above the middle of the head. In turret- 

 clocks, where there is more room to get at the adjusting work, it may be done by screwing 

 long eccentric pins into the bottom of the arms (which should come down just beyond the 

 range of the fly) with nuts : then as you turn the pins the eccentricity does the adjustment for 

 beat. In all cases there should be somewhere on the clock-frame a couple of fixed banking- 



