Experiment in Search of Action of one Crystal on another. 121 



the eyeballs correctly in any desired position the exercise of peripheral 

 apparatus of muscular sense is required, the only possible channels 

 under the above conditions would seem to be deep branches of the Vth 

 nerve or the Illrd, I Vth, and Vlth so-called " motor " nerves them- 

 selves. As previously stated, the former are by both my earlier and 

 later degeneration experiments excluded. The latter, therefore, are 

 the only ones remaining, for the superficial branches of the Vth and 

 the retinae are put out of action by the conditions of experiment. 



I am indebted to Mr. E. E. Laslett for carrying out the observations 

 with me. Details regarding the methods employed and the results 

 obtained will be given in a completer paper written in conjunction with 

 him. 



" An Experiment in Search of a Directive Action of one Quartz 

 Crystal on another/' By J. H. POYNTING, Sc.D., F.R.S., and 

 P. L GRAY, B.Sc. Eeceived September 27, Ptead November 



17, 1898. 



(Abstract.) 



A quartz sphere, O9 cm. diameter, weight T004 grams, was sus- 

 pended by a long quartz fibre so that its time of vibration was about 

 120 seconds. A second quartz sphere, 6'6 cm. diameter, weighing 

 399-9 grams, with its centre on a level with that of the first and 

 5-9 cm. from it, was rotated continuously in a period of 115 seconds in 

 one series, and in a period of 230 seconds in another series of obser- 

 vations. 



The axis of the smaller sphere was horizontal and perpendicular to 

 the line through the centres. Any directive action should manifest 

 itself as a periodic couple, producing forced oscillations in the smaller 

 sphere. 



If the ends of the axis of a quartz crystal are indistinguishable the 

 couple should go through its values in half a revolution of the larger 

 sphere. This is termed the " quadrantal " couple, and to test for it 

 the time of revolution was 230 seconds, or nearly double that of the 

 suspended sphere. If the ends of the axis are poles, like those of a 

 magnet, the couple should go through its values only in a complete 

 revolution. This is termed the " semi-circular" couple, and to test for 

 it the time of revolution was 115 seconds, or nearly equal to that of the 

 suspended sphere. The position of this latter sphere was read by means 

 of mirror and scale every 11 '5 seconds, i.e., at ten equidistant phases of 

 the 115-seconds period. By taking a large number of periods, the 

 mean reading for each phase should be freed to a great extent from other 

 periodic motions and accidental disturbances, and a 115-second vibra- 

 tion should, if it existed, be rendered evident. 



L 2 



