376 Messrs. Richards and Trowbridge on the Effect of Great 



Sometimes the mercury gets into a lethargic condition; hut 

 it can always be roused by mechanical agitation of the surface. 

 iSlow let the current be kept on for a few seconds ; the negative 

 globule sends forth a tentacle towards the positive globule, 

 the length of the tentacle depending upon the current and 

 the distance between the globules. Under favourable cir- 

 cumstances it may extend from corner to corner, and thus 

 establish contact ; or fissure may occur, the tentacle breaking 

 into spheroids ; and these spheroids may cross over between 

 the globules. This is the order of things usually to be 

 observed, but the action is sometimes erratic. 



Let us now bring back the scattered globules of mercury 

 to their respective corners, and distribute a few isolated 

 spheroids in the interspace. In addition to the effects 

 previously noticed at the terminal globules, we now see that, 

 when the current is applied, each intermediate spheroid 

 extends a " finger ' 5 towards the positive globule. This is the 

 process of mobile coherence ; the short " fingers," or long 

 " tentacles," form links between consecutive spheroids, and 

 finally a complete conducting circuit is established. 



By successive applications of the current, any elongated 

 bodies of mercury between the terminal globules can be made 

 to creep along like caterpillars ; the successive forward 

 motions of the tentacle, or tail, cause a corresponding retro- 

 gression of the globule as a whole. 



Any small spheroids scattered about the dish may be urged 

 in a direction depending upon the direction of the successive 

 current impulses; and a " finger " will always appear on the 

 side towards the positive electrode. So that by choosing a 

 convenient stray spheroid, and operating a battery-reverser 

 as a transmitting- key, a telegraphic receiver is improvised 

 from no other apparatus than a drop of mercury and a little 

 oil. By some such means the awakening genius of primi- 

 tive man may have contrived all the subtle machinery of a 

 telegraph-instrument upon the smooth surface of an oyster- 

 shell. 



L. The Effect of Great Current -Strength on the Conductivity 

 of Electrolytes. By Theodore William Richards and 

 John" Trowbridge *. 



IN our paper on the temperature and ohmic resistance 

 of gases during the oscillatory electric discharge f, 

 we have described a method of determining resistance by 



* Communicated by the Authors, 

 t Page 349, supra. 



