322 ■ PHILOSOPHICAL TKANSACTIONS. [aNNO I739. 



Further Observations and Experiments concerning the two Clocks ahovementioned. 



By the Same. N" 453, p. 128. 



The seemingly different effects, which the two clocks had on each other, 

 Mr. Ellicott accounts for as follows. 



The manner in which the motion is commimicated to the pendulum at rest, 

 he conceives to be thus: as the pendulums are very heavy, when either of them 

 is set a going, it occasions by its vibrations a very small motion, not only in the 

 case the clock is fixed in, but, in a greater or less degree, in every thing it 

 touches ; and this motion is communicated to the other clock, by means of the 

 rail, against which both the cases bear. The motion thus communicated, which 

 is too small to be discovered but by means of some such-like experiments as 

 these, may be judged by many, insufficient to make so heavy a pendulum de- 

 scribe an arch of 2°, or large enough to set the work a going ; and indeed it 

 would be so, but for the very great freedom with which the pendulum is made 

 to move, arising from the manner in which it is hung. This appears from the 

 ^erysm air weight required to keep it going, which, when the clock was first put 

 together, was little more than 1 lb. And if the weight was taken off, and the 

 pendulum made to swing 2°, it would make J 200 vibrations before it decreased 

 half a degree, so that it would not lose the 3000th part of an inch in each 

 vibration. Indeed if the weight was hung on, the friction would be increased, 

 and the pendulum would not move quite so freely ; but even in that case it was 

 found to lose but little more than the 2000th part of an inch, or about 3 

 seconds of a degree, in one vibration ; and therefore if the motion communi- 

 cated to it from the other, will make it describe an arch exceeding 3", the vi- 

 brations must continually increase till the work is set a going. And that the 

 motion is communicated in the manner above supposed, is confirmed by the 

 following expeciments : 



A prop was set against the back of the case of N° 2, to prevent its bearing 

 against the rail ; and N° 1 was set a going ; then observing them for several 

 hours, Mr. E. could not perceive the least motion communicated to N°2. He 

 then set both the clocks a going, and they continued going several days ; but 

 he could not find they had any influence on each other. Instead of the prop 

 against the back of the case, he put wedges under the bottoms of both the 

 cases, to prevent their bearing against the rail ; and stuck a piece of wood be- 

 tween them, just tight enough to support its own weight. Then setting N° 1 

 a going, the influence was so much increased, that N° 2 was set a going in less 

 than 6 minutes, and N° 1 stopped in about 6 minutes after. In order to try 



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