304 Mr R. Adie on Electrical Experiments. 



long sustained in Smee's battery, the galvanometer indicated only 9° 

 at the end of the first 48 hours, then the decrease in the electrical 

 current is much more slow ; and it required 8 days' continued action 

 for the galvanometer to fall through the remaining 9°. 



With joints disposed like fig. 3, I made a number of experiments 

 to try the effect of electrical currents on them ; but as all of the re- 

 sults obtained could be accounted for, by the influence of the heat 

 which electricity developes in passing across those joints, it seems to 

 me to be unnecessary to enter into the details of the experiments in 

 question. 



41. There are some remarks on voltaic phenomena by Professor 

 Grove and Mr Mackerell,* which may be thought at variance with 

 the fact of the unequal heating of any medium traversed by an elec- 

 trical current, as I have above attempted to prove. For Professor 

 Grove has shewn that in rapid decompositions, a more brilliant com- 

 bustion is observed at the negative pole than at the positive ; while 

 in my experiments the temperature of the negative pole is always 

 the lowest. This apparent contradiction can be reconciled, when 

 the necessary conditions for the appearance of combustion at the 

 poles of a battery are examined. I have always found that the de- 

 composing surface must be enveloped in gas when the spark appears ; 

 it is while the electricity is crossing this gaseous atmosphere that 

 combustion takes place (see 1st series 2Q.) A consequence of this is, 

 that where the largest volume of gas is evolved from a given super- 

 ficies, there the sparks should be the most brilliant. Where acidu- 

 lated water is decomposed, there is double the volume of gas elimi- 

 nated at the negative pole, compared with the gas at the positive 

 pole ; hence the greater brilliance in Professor Grove's experiments, 

 when the voltaic circuit is completed by dipping the negative wire ; 

 for the same surface of wire has to evolve twice the volume of gas 

 which it had to do when the contact was made by dipping the positive 

 wire into the acid solution. By employing a positive wire of half the 

 section of the negative wire, the difference noticed disappears. The 

 crackling noise stated by Professor Grove to accompany these rapid 

 decompositions, becomes much sharper when sulphuric acid S. G. 

 1850, is substituted for acidulated water. It appears to me to bo 

 occasioned by the rapid formation of gas bells, exactly like steam 

 bells formed in pure water boiling in a smooth glass vessel. The 

 noise in both cases is very similar, and with sheathed poles the bells 

 of gas may be seen to quit the pole at each sharp sound heard.t 



* See Elec. Mag. pp. 121 and 277. 



t The experiments with platiua and copper capsules detailed above; 

 were performed during last winter, when the ground was partially covered 

 with melting snow. The temperature of that season was unfavourable 

 for secondary decompositions, and as I wished to obtain greater changes 

 in the temperatures with copper poles decomposing sulphate of copper, I 

 returned to them in midsummer, and employed small capsules of i a su- 



