198 Mr Herschel on the Mechanical Effects, §c. 



indeed, from the physiologist, when we consider the bearing 

 which. the discovery of mechanical powers, exerted by electri- 

 city, may, one day, have on that most mysterious of physiolo- 

 gical problems, the origin of muscular motion. 



Although no visible effect in producing, suspending, or al- 

 tering the radiating currents appeared in my experiments to 

 arise from the presence of powerful magnets, yet, as it seemed 

 not impossible, that the mutual action of the elementary elec- 

 tric currents traversing the mercury and the supernatant li- 

 quid, (probably with very different velocities,) might deter- 

 mine motions in the media transmitting them, and thus be at 

 the bottom of the whole, I resolved to put this to the test of 

 experiment, as follows : I divided a saucer into two equal 

 cells, by the thinnest film of mica I could detach, and secured 

 the insulation of the cells from each other by sealing-wax. I 

 then filled them to the same height with perfectly clean dry 

 mercury, and having prepared two piles of 10 pairs each, in 

 full action, I completed the circuit of the one in the one cell, 

 and of the other in the other. But whether the currents pass- 

 ed in the same or in opposite directions, — whether the con- 

 tacts were made close to the mica or at a distance from it, — 

 whether both piles were in action, or one only, — whether their 

 actions were equal, or one was purposely rendered feebler than 

 the other, or totally abstracted, or united to the other, not the 

 slightest motion was produced in either cell. When the two 

 currents were transmitted at once through sulphuric acid over 

 mercury, their effects seemed to be merely superposed, no ap- 

 pearance of interference arising ; but each molecule of the 

 mercury obeying their joint impulse, apparently according to 

 the usual mechanical laws of the composition and resolution of 

 motions. It is not, therefore, in the magnetic vortices that 

 we are to look for the cause of these motions, but in some new 

 and singular action of electricity, to develope which more fully 

 will require numerous and delicate experiments. 



I have the honour to remain, 



Dear Sir, very truly yours, 



J. F. W. Herschel. 



London, Jan. 21, 1825. i 



