Book IX. Mechanic Powerr. 193

Problem. VII.Another way of fitting 4 Pendulum to à Cloch.

Fig. 3H we will deſcribe the way moſt in uſe of fit-ting Pendulums to Clocks, the ſerpentine orencountring wheel, muſt be placed in an Horizontal ſite, andthe beam of the Ballance alſo ſtretcht out Horizontally on theſame; the wheel furniſnt with jagged teeth, muſt have its num-ber unequal to this, that two little flaps, or wings, of the Beamof the Ballance, may lay hold on the teeth by turns, accordingto the uſual manner, which little wings ought therefore ſo tobe joined to the beam of the Ballance, that their planes makea right angle, and the Axis of the beam ought to be extendedpreciſely through the centre of the Wheel ; but becauſe if thebendulum be immediately join d to the beam of the ballance,its weight will burden it too much, therefore a handle is addedto the beam, boared through in the extream point, to whichhole is fixt a rod hanging at liberty that it may eaſily agitate.But you muſt take care that the lower little arm poſſeſs amiddle ſite between each little wing of the beam of the Bal-lance, leſt one vibration of the pendulum be greater than ano-ther, and make the motion very incongruous and lame; in thereſt obſerve the precepts already delivered; ſome fix a Globeunmoveable on the end without any Screw , moving the cen-tre of the Spear or Wire, they raiſe it. or depreſs it to reducethe vibrations to the exact meaſure of time, for when the cen-tre is raiſed, the pendulum runs through a leſſer arch, andſooner diſpatches each vibration, ſpecially becauſe tis reſiſtedby a leſſer impulſe, and it makes the vibration ſlower, if it bedepreſt for the contrary reaſons; yet you muſt take care thatthe centre be not beneath the axis, nor that it be elevated muchabove it; laſtly, the length of the little arms are determinedby practice, and by the wheels.

Problem