\) 





290 Dr. J. H. Vincent on 



discrepancies between theory and experiment. In default of 

 a more perfect theory, it will be of no small interest to see 

 how far the aforesaid theory can explain the correlation of 

 strain and stress in magnetism ; we intend to continue similar 

 investigations on the Wiedemann effect, and see how tho 

 mutual relations between the strains due to magnetization 

 and the effects of stress on magnetization can be traced. 

 Physical Laboratory, Tokyo, 

 March 15th, 1898. 



XXVII. On the Photography of Ripples. — Third Paper. 

 By J, H. Vincent, 1).Sc, A.R.C.Sc* 

 ,/ [Plates II1.-V.] 



TT^HE present paper deals with some further experiments on 

 JL wave-motion, which have, as before, been photographi- 

 cally recorded. In the first two papers f the apparatus used 

 was described. The work has been continued with the second 

 form of apparatus, but it has been necessary to re-arrange the 

 whole, as the induction-machine and tuning-forks suffered so 

 much from the damp that the former finally refused to work 

 and the latter required constant attention to prevent rusting. 

 It was therefore decided to set up the apparatus in another 

 portion of the laboratory ; while this was being done the 

 induction-machine was repaired. The room in which the 

 experiments were continued is at the top of the building, but 

 the unsteadiness was overcome by suspending the trough by 

 a rubber cord. 



The floor of this room being unsteady, it was necessary to 

 stop the motor and induction-machine some seconds before the 

 spark was allowed to pass ; otherwise the motion of the floor 

 would cause objects attached to the forks to give rise to dis- 

 turbances on the mercury surface. 



Some alterations were made in the apparatus. The first 

 spark-gap was reduced very considerably in width and was 

 about 2 millim. across. With this alteration it was found that 

 much larger apertures of the lens-stop could be used without 

 *any ill-effects on the photographs. This spark-gap was 

 short-circuited by a coil, about 8 centim. in diameter, of a 

 dozen turns of rubber-covered wire. The other electrical 

 arrangements were -similar to those described in the first 

 paper. Four gallon Leyden jars were used, and the whole 

 electrical circuit was insulated. The first spark-gap was 



* Communicated by Professor J. J. Thomson. 



t Phil. Mag. June 1897; Proc. of Phys. Soc, Julv 1897; Phil. Mag., 

 Feb. 1898. 



