188 Mr. G. J. Knox on the Direction and Propagation 
ture of sulphur was, that it was a compound of small quan- 
tities of oxygen and hydrogen, with a large quantity of a 
basis, that produces the acids of sulphur in combustion, and 
which, on account of its strong attraction for other bodies, will 
probably be difficult to obtain in its pure form*.” To put the 
question beyond any further doubt, I will mention some ex- 
periments which I tried in the laboratory of the Royal Dublin 
Society in the year 1837, having had, through the kindness of 
Professor Davy, a galvanic battery of sixty pair of plates, five 
inches square, put at my disposal. 
When fused phosphorus, sulphur, selenium and iodine, 
were submitted separately to the action of this battery charged 
with a strong acid solution, they conveyed the electrical cur- 
rent freely during the whole time, giving a spark whenever 
contact was broken ; yet at the end of two hours they showed 
not the slightest trace of decomposition, no gas being evolved 
at either pole, which would have been the case had there been 
any water present. 
Having by these experiments shown the direction of pro- 
pagation of the electric force, I will now consider the source 
from which it originates in the voltaic pile, the mode of its 
transfer, and its sustaining principle. 
Sir H. Davy’sf opinion that the contact of the metals was 
the primum mobile of voltaic excitement, having been proved 
by Dr. Faradayf to be erroneous, chemists are now pretty 
generally agreed that the electrical force developed in the vol- 
taic pile is due altogether to chemical action, concerning which 
there are different opinions; of these, I will mention two, which 
are the most applicable to the present argument — Dr. Fara- 
day’s§ and Mr. Becquerel’sH. The former supposes that the 
development of electricity is due to decomposition alone, and 
in no case to the chemical union of bodies ; while the latter 
contends that it is due to both, and in proof of his opinion 
shows that when an alkali unites with an acid, with a neutral 
salt, and in fact with any solution whose natural state is with 
regard to it electrically negative, a current of electricity will 
flow from the alkali to that solution. Sir H. Davyf has taken 
a different view of these experiments from Mr. Becquerel, 
supposing that the electric current is produced by the action 
of the acid or alkali upon the platinum plates ; but the latter 
has shown that the electrical current is produced equally when 
♦ Bakerian Lecture, 1809. f Phil. Trans., Bakerian Lecture, 1826. 
I Eighth Series, (880). § Eighth Series, (927) (928). 
II Tom. ii. from page 77 to 81. % Phil. Trans., Bakerian Lecture, 1826. 
