616 Prof. Barton and Miss Browning on 



P may still be transmitted through the connectors BB' and 

 CC to the pendulum-bob R. Further, the connector DD' 

 may tend to force in extra vibrations, so that four, or more 

 vibrations may be felt by each bob. 



(2) That the bridle droop being different for one pendulum 

 may also complicate matters. 



The bridle droops do not enter into these experiments in 

 exactly the same way as in those of the Double-Cord Pen- 

 dulums, "Coupled Vibrations" (Phil. Mag. Oct. 1917); for 

 in that the bridle droop directly determined the length of the 

 oscillating pendulums. 



Suppose the pendulum P is considered, and the one con- 

 nector at BB'. Then the two oscillations possible to this 

 pendulum, if others are not forced upon it, are : — 



(a) One about AE ; 



(b) One about BE if B is held stationary. Now if the 

 bridle AFE is altered, but the connector B is so adjusted 

 that BE makes the same angle with the horizontal, then the 

 period of the oscillation of the pendulum about this position 

 is unaffected. For small oscillations, the effective length would 

 be found by producing PF upwards until it met the line 

 joining BE in B . 



For this arrangement it is not easy to write down definite 

 values for the couplings. However, from general consi- 

 derations, it is seen that, if BB' and CC ; are near AA", and 

 DD' to EE", the couplings will all be small. The coupling 

 between two only will be large if those are connected near F, 

 and the others near A or E. 



The early experiments were done with the apparatus as 

 described. Later the connector CC was removed, and 

 results obtained for certain couplings were found to be 

 similar to those obtained when using three connectors. 



IV. Photographic Records of Vibrations. 



Nine photographs of traces were taken with the three 

 connectors in use (Pis. XL & XII.). Six others with only 

 the two connectors BB' and CC 7 , but otherwise the same 

 arrangement (PI. XIII.) 



For details of the lengths mentioned in the table reference 

 must be made to figures 1 and 2. The masses of the bobs in 

 these experiments were all the same. and equal to 660 gms. 

 In all the experiments the total depth of the bobs below AE 

 was kept constant and equal to 140 cms. The distance between 

 AE was 180 cms. Tbe positions of B, 0, D, F, and G will 

 now determine the whole of the system. 



