,1861.] 219 



tion of hydrogen. It is essential that the electric power be within 

 proper limits, otherwise the phenomena will not occur, and I have 

 therefore found it very convenient to employ a wind-up battery, the 

 plates of which can be instantly immersed to any desired depth in the 

 exciting liquid. The one I have used in nearly all the experiments 

 described in this paper consists of ten Smee's elements, each plate 

 being 7\ inches wide and 11^- inches deep, single zincs and single 

 silvers, and capable of being immersed about 9 inches in the exciting 

 liquid ; it is sufficiently large to produce the phenomena in rings 

 of mercury 8-J inches diameter and -J-th of an inch wide : with small 

 rings of mercury the plates are immersed only f ths of an inch deep. 

 It is advisable in all cases to produce the sounds by nearly the mini- 

 mum of electric power, because they are then generally more uniform 

 and more prolonged. The introduction of a coil of stout copper wire 

 (containing a soft iron core) into the circuit will considerably assist 

 the production of sounds if the cells are few in number. 



5. Instantly on passing the electric current, a series of small ele- 

 vations, which I shall term vibrations or crispations, occur upon the 

 surface of the annular portion of mercury, and impart to it the ap- 

 pearance of a series of transverse ridges, all radiating from the centre 

 of the vessel* ; and these elevations or crispations are accompanied 

 by definite sounds very similar to the humming of a large bee, and 

 capable of being heard under favourable circumstances at a distance 

 of upwards of 50 feet. The sounds are evidently produced by the 

 vibrations. 



6. These elevations are exceedingly definite and uniform in size ; 

 apparently all of them are at exactly the same distance asunder at 

 any given moment if the mercury is undisturbed by other causes ; 

 the distance varies under different circumstances from about -Jth 

 of an inch to a distance so small as to be scarcely distinguishable by 

 the unassisted eye. The apparent distance asunder of each elevation 

 is probably half the distance of the actual vibrations, because the 

 mercury is raised and depressed with great rapidity at each of those 

 spots : while one spot is in a state of elevation, the next adjoining 

 one is depressed ; and while the former spot is depressed, the latter 

 is elevated, and so on alternately with such great rapidity as to pro- 



* The appearances and their beauty cannot be satisfactorily represented by 

 sketches. 



R2 



