230 [Dec. 12, 



in the surface of the negative mercury parallel to the boundaries of 

 its surface, i. e. circular furrows, "one within the other ; on immersing 

 the plates deeper, transverse furrows occur superimposed upon the 

 others, and thus give rise to the little heaps or elevations (5, 6, 7) of 

 mercury ; the sounds do not occur until the latter furrows are 

 produced. 



Similar effects may be produced by mechanical means : if a watch- 

 glass containing a little mercury is affixed by means of sealing-wax 

 to a flat and horizontal strip of window-glass about 8 inches long and 

 3 inches wide, supported firmly at its ends, and vibration be induced 

 in the mercury by resting the end of a vertical glass rod upon the 

 strip of glass, and drawing wet fingers with pinching pressure down 

 the rod, and the vibration be gradually augmented, a similar series of 

 changes will be produced by the gradual increase of mechanical 

 power to those produced by a gradual increase of electric power. 



Influence of the Vibrations upon the Electric Current. 



33. It was found, by interposing a galvanometer (with a short 

 and thick wire) in the circuit, that when the vibrations ceased, as 

 they sometimes do very suddenly, the quantity of the electricity 

 passing was instantly diminished, the needles shifting from 22 degrees 

 to 18 an effect, no doubt, of exhausted solution accumulating at the 

 electrodes. To ascertain if the vibrations of the mercury and electrolyte 

 made the electric current intermittent, the current from three Smee's 

 elements, 7|- inches wide, immersed 8^- inches in the exciting liquid, 

 was allowed to circulate through the primary wire of a Ruhmkorff s 

 induction-coil (kindly lent to me by Professor G. G. Stokes) (the 

 break-hammer being excluded) and the phonetic liquid, the ends 

 of two fine platinum wires from the secondary terminals being in 

 contact with a drop of solution of iodide of potassium, but no signs 

 of decomposition of the iodide could be detected with the aid of an 

 eye-glass ; on applying, however, the secondary terminals to my 

 tongue, rather sharp shocks were experienced, and could be very 

 distinctly felt with the damp fingers of my two hands ; also a piece 

 of iron of proper size, and suitably held near or in slight contact with 

 the iron core of the coil, could be distinctly felt to vibrate. If only 

 two of the elements, immersed 8^- inches, were employed, and the 

 mercury electrodes reversed for a short time and then returned to 



