﻿240 Intelligence and Miscellaneous Articles. 



__2pL = 0*0081, or twenty-two times the current produced by the 



machine in the human body. 



Such numbers lead to the conclusion that, though far more pro- 

 ductive machines than the above may, and probably will, be con- 

 structed by increased velocity of rotation, a larger number of places 

 of decomposition, and of combs, yet they cannot be thought of as a 

 substitute for constant currents, or in general for actions which are 

 proportional to the intensity. It is different with actions which are 

 proportional to the square of the intensity, like the thermal actions 

 observed by Holtz and Poggendorff, or with the physiological which 

 are produced by intermittent currents, and depend upon the rapidity 

 of the change of current. By the possibility of resolving the mean 

 current of the machine, by means of an interposed layer of air, into 

 parts of greatly increased intensity, actions may be obtained which, 

 under certain circumstances, may approach to galvanic ones. — Pog- 

 gendorff' s Annalen, No. 9, 1868. 



ON THE INTERFERENCE OF LIQUID WAVES. 

 » BY M. LISSAJOUS. 



The interference of liquid waves may be demonstrated by means 

 of an apparatus which is both simple and easy to construct. It 

 consists of two horizontal "diapasons fixed to the same support in 

 such a manner that the four branches are in the same horizontal 

 plane. Each diapason is provided with a vertical point ; these two 

 dip at a distance of a few centimetres in a bath of mercury or 

 water. 



If one of them be made to vibrate, the disturbances communicated 

 to the liquid produce waves which are propagated with greater or 

 less rapidity, according to the nature of the liquid. If both be si- 

 multaneously disturbed, a system of fixed waves is formed between 

 the two points which are perfectly distinguishable by the play of 

 light which they produce. 



When the two diapasons are not in perfect unison, the waves are 

 seen to be slowly displaced ; and it can readily be proved that they 

 move towards the lowest one. 



Thus, by means of the eye, not merely the discordance of two 

 vibrating apparatus maybe recognized, but also its direction. 



This second experiment furnishes an ocular demonstration of the 

 cause of beats. 



It is also possible to use this method for comparing the velocity 

 of the propagation of waves on the surface of different liquids. 

 — Comptes Rendus, December 24, 1868. 





