82 On the Mutual Influence 



Q\ inches long, weighing f- ounce, was employed. The arc of 

 vibration of No. 2, after 5 minutes, was rather more than 6" — 

 that of No. 1, 5 0, 45' 



Exp. 12. — In experiment 12, a brass chain, about 9^ feet long, 

 weighing 5^- ounces, was found to produce no sensible effect. 



Exp. 13. — In experiment 13, I employed a piece of Manila 

 rope, about 14 feet 2 inches long, weighing 5 J ounces. After 5m., 

 pendulum of clock 2 showed an arc of vibration of 30'; that 

 of clock 1 vibrated through 5° 40' 



Exp. 14. — In the last experiment which I shall refer to, I used 

 a bar of lead weighing 24^ lbs., about 18 inches long. At the 

 expiration of 5m., the pendulum of clock 2 oscillated through an 

 arc of 31' 30" ; that of 1 through 5°40/ 



This is the heaviest upper medium we have yet considered : but 

 the effects produced are very small compared with others of 

 lighter material. In summing up the results of these experiments, 

 I arrive at the following conclusions : — 1st, that this observed 

 phenomenon is not to be accounted for by any mutual attraction 

 between the pendulums. 2ndly, that there is not sufficient evi- 

 dence to make it probable that it is due to any direct statical 

 ressure. 3rdly, that it may reasonably be accounted for on the 

 supposition of " imperceptible vibrations" propagated through 

 some connecting medium between the clocks, and that the extent 

 of the effect produced, depends upen the nature of the medium 

 employed. 



The experiments appear to prove, that in order to ensure their 

 success,it is necessary there should be a medium between the feet of 

 the clocks as well as between the tops ; and if we examine 

 the results obtained by placing different media between the tops 

 of the clocks, we perceive that they are not solely dependent 

 upon the weight of the medium. We observe that the same three 

 solid boards placed loosely one on the other, give different results 

 when they are firmly secured together. We observe that this 

 compact wooden mass produces much larger effects than a bar of 

 lead nearly double its weight. 



We observe that whilst a light deal rod weighing six ounces 

 only, causes a perceptible effect on clock 2, none is produced by 

 a chain of nearly the same weight ; yet slightly perceptible effects 

 are produced by a piece of rope of nearly equal weight. 



The brass tube, weighing 13 ounces, causes larger oscillations 

 than other media of greater weight ; and lastly we observe that 

 the three bars of pine whose lengths and weights are as the 

 numbers 1, 2, 3, give nearly the same results, and that their 

 magnitudes, though not proportional, yet appear to depend upon 

 the length of the bars. 



