48 Mr . Davy’s Lecture on some 
of being immersed in the gold cones, expecting (if any) only 
a very slight change of temperature ; I introduced a drop of 
solution of sulphate of potash into the positive cone : the de- 
composition instantly began: potash passed rapidfy over into 
the negative cone, heat was immediately sensible ; and in less 
than two minutes the water was in a state of ebullition. 
I tried the same thing with a solution of nitrate of ammonia,, 
and in this instance the heat rose to such an intensity as to 
evaporate all the water in three or four minutes, with a kind 
of explosive noise ; and at last actual inflammation took place, 
with the decomposition and dissipation of the greatest part 
of the salt.* 
That the increase of the conducting power of the water by 
the drop of saline solution had little or nothing to do with the 
effect, is evident from this circumstance. I introduced a quan- 
tity of strong lixivium of potash into the cones, and likewise 
concentrated sulphuric acid, separately, which are better con- 
ductors than solutions of the neutral salts ; but there was very 
little sensible effect. 
The same principles will apply to all the varieties of the 
electrical apparatus, whether containing double or single 
plates ; and if the ideas developed in the preceding sections 
be correct, one property operating under different modifica- 
tions is the universal cause of their activity. 
* In this process ammonia was rapidly given off from the surface of the negative 
cone, and nitrous acid from that of the positive cone, and a white vapour was pro- 
duced by their combination in the atmosphere above the apparatus. 
