Relations of Electricity with bodies in the spheroidal state. 445 



200. I shall conclude by relating some experiments which 

 appear to me to have a certain practical importance. M. 

 Thury, my assistant during the winter session, remarked that 

 water let fall upon a heated copper capsule only assumes the 

 spheroidal state for some seconds, and generally not at all when 

 the surface is coated with deutoxide of copper. I immediately 

 suspected that this was not a property peculiar to the oxide, 

 but an effect attributable to the rough state of the surface, as 

 M. Boutigny has remarked*. Direct experiments have shown 

 that this opinion is well-founded. 



201. A platina capsule was half coated with a paste formed 

 of oxide of zinc and water, and raised to a dull red. It then 

 presented the curious appearance of two surfaces, one of which, 

 being metallic and brilliant, spheroidalized instantaneously the 

 pure water which now only evaporated with extreme slowness; 

 whilst the latter, rough and of a beautiful canary-yellow, con- 

 verted no less suddenly into vapour the drops of water which 

 were projected on to it. 



202. The carbonate of protoxide of iron, reduced to the 

 state of peroxide by calcination, behaves like the oxide of zinc. 

 The colour and'the chemical nature of the deposit do not 

 therefore take any part in the phenomenon. 



203. English rouge mixed up with water covers platina, 

 but it does not absolutely prevent the spheroidal state from 

 being produced : its action seems to be limited to diminishing 

 considerably the duration of the evaporation f- 



204. The red oxide of manganese, obtained by the pro- 

 longed calcination of the peroxide, is still less destructive of 

 the spheroidal state than the colcothar : moistened with cold 

 water it adheres much less to metallic surfaces. 



205. The colourless syrup of sugar readily assumes the 

 spheroidal state on platina. The drops appear at first opake, 

 especially if they are large, from a number of small bubbles 

 of gas traversing them ; they subsequently become beautifully 

 transparent, and remain frequently immoveable, similar to 

 nearly spherical glass lenses. Lastly, when the syrup has 

 attained the maximum of concentration, it enters into a violent 

 state of ebullition, without however spreading over the cap- 

 sule, or moistening it ; it changes into caramel, passing from 

 a yellow to a brown colour, and finally leaves a bulky ball of 

 porous carbon. 



206. If the heat is diminished at the moment when chemical 



* Loc. tit. pp. 48, 56 and 76. 



\ M. Muncke has already observed, that a plate of iron oxidized by 

 contact with air at a white red heat ceases to spheroidalize water which is 

 poured on it. — Gehler's Phys. fVorterbuch, 2nd edit., vol. x. p. 490, 1841. 



