4:54 Prof. Barton and Miss Browning on 



a 



pendulum with heavy bob D. On an adjacent cord AGH 

 was hung at Gr a similar pendulum, with bob F about equal 

 in mass to D. This pendulum was made to affect the reso- 

 nators by means of a wooden connector at L. This connector 

 is far from both the large driving pendulums, and so the effects 

 of the coupling between them were always small and never 

 obtruded themselves. 



Thus the two forcing pendulums or drivers could be of 

 various lengths at will, and so subject the resonators to the 

 corresponding double harmonic impressed forces. For each 

 one was sufficiently connected to the resonators while the 

 two were almost free from action and reaction on each other. 

 The experiments consisted in adjusting the lengths of the 

 drivers, starting their oscillations, and then taking either 

 flash photographs or time exposures of the resonators. 



It should be noted that the effective lengths of the driving- 

 pendulums are DE and FI respectively, those of the reso- 

 nators being typified by JK. 



Results. — PlateV. figs. 1-6 shows the effects obtained on the 

 responding pendulums with plane paper cones by two drivers 

 of distinctly different periods and kept of the same lengths 

 throughout. The responders were highly damped, and soon 

 settled to their steady state corresponding to their forced 

 vibrations only. It is highly instructive to watch the reso- 

 nators in these cases. They show two distinct humps or 

 places of maximum resonance as exhibited in fig. 1, which is 

 a time exposure. But also, when watching them, the quick 

 vibrations of those pendulums in tune with the short driver 

 are in striking contrast to the slower vibrations of those in 

 tune with the longer driver. Thus the vibrators exhibiting 

 the two humps are almost always out of phase. But near 

 each hump or maximum there is the usual state of ordered 

 phase relation corresponding to the resonance in question. 

 These effects are partly indicated by the flash photographs 

 of figs. 2-6. These five reproductions illustrate one of 

 the effects shown in the paper already cited. [Namely, that 

 we have sometimes a hump all on one side of the central 

 line, and sometimes the quasi-cubic with smaller humps one 

 on each side. It should be noticed that in figures 1-6 of 

 this Plate the resonance is not sharp but spreads over a con- 

 siderable distance up and down owing to the verv strong 



• ^ JO 



damping of the resonators m use. 



PlateV. figs. 7-12 shows the effects obtained when the paper 

 cones each carried a ring of copper wire and so were much 

 less damped. Consequently the resonances are much sharper 

 instead of being widely spread as before. This is best seen 

 in the two time exposures, figs. 9 & 10. The flash 



