442 Prof. E. Wartmann's Seventh Memoir on Induction : 



rheometer placed in the circuit shows that this is the case. 

 This is an excellent proof of the character essential to the 

 spheroidal state, that the drop does not touch the heated sur- 

 face. The excessively thin and very hot layer which separates 

 it is not conducting. It would be interesting to ascertain the 

 relation which exists between its isolating power and its tem- 

 perature, with various liquids placed on supports of different 

 natures. 



191. When one of the rheophores touches any portion of 

 the capsule externally to the liquid, and the other is immersed 

 in the liquid and in contact with the metal, the passage of the 

 current is established, and the drop evaporates rapidly pro- 

 ducing abundant bubbles accompanied by a certain sonorous 

 vibration. This phenomenon ceases as soon as the voltaic 

 circuit is opened. It is presented not only when the extre- 

 mity of the rheophore rests on the capsule below the liquid 

 which it traverses, but also when the contact takes place out- 

 side the lower surface of the drop. In both cases the two 

 somewhat thin polar wires are heated for a great length till 

 they cannot be longer handled. The heat thus disengaged 

 is the cause of the bubbles of vapour. This may readily be 

 observed by immersing in pure spheroidalized water a very 

 massive silver wire. A few instants after its contact with the 

 capsule ebullition is perceptible, resulting from its conducti- 

 bility for heat*. This phenomenon has considerable analogy 

 with that of the combustion of albumen under the influence 

 of very powerful currents (139.). 



192. Acidulated water was replaced by mercury, the con- 

 ductibility of which is still greater. Contrary to the assertion 

 of Fischer, this body passes into the spheroidal state provided 

 it is reduced to very small masses. A rather large drop which 

 falls on a platina capsule at a dull red heat, boils at first in a 

 very remarkable manner. Its surface is furrowed with a 

 thousand wrinkles which deprive it of its mirroring aspect, 

 and it rapidly evaporates with a sort of crepitation. While 

 it is in this state, it touches the platina metallically, for it con- 

 ducts the current of the pile. All at once the small quantity 

 of mercury which remains recovers its brilliant polish : it be- 

 comes round in a nearly geometric sphere, the noise ceases, 

 and the evaporation continues with very great slowness : the 

 drop is then electrically isolated from its support. 



193. The discontinuous currents remained to be examined. 

 To study their influence on the spheroidal state, I produced with 

 the five Grove's pairs instantaneous currents of very great 



* An analogous observation is mentioned by M. Boutigny, loc. cit. pp. 66, 

 70 and 105. 



