PHYSICS OF NINETEENTH CENTURY 181 



it supposes that individual molecules, the velocity 

 of which is subject to continual alteration owing to 

 collisions, cannot be followed and separated into fast- 

 moving and slow-moving groups, for, as Maxwell 

 pointed out, such a power would enable diffused 

 energy to be reconcentrated. Nevertheless, in the 

 conditions of Nature as then known, the conclusion 

 stood; the energy by which we live and move was 

 seen to be becoming continually less available, the 

 iron hand of mechanical necessity stretched out to 

 grasp and crush the life of the Universe. 



The steam engine was developed by practical men 

 to meet industrial needs, and owed little, except 



The Rise of m ^ S ^ ater sta es > * o tne ne ^P f P ure 

 Electrical science. But, as regards the other 

 Science. g rea t physical agency of modern civilisa- 

 tion electricity the case was very different. Here 

 the practical applications followed, and were a direct 

 consequence of, the researches of men who sought for 

 knowledge alone. Modern electrical science began with 

 the discovery of the phenomena of " galvanism " or 

 current electricity by Galvani in 1786, and Volta of 

 Pavia in 1800. Volta's cell, from which he produced 

 the first electric current, consisted essentially of two 

 plates of unlike metal, placed in the solution of an acid 

 or a salt. This apparatus was found to show effects 

 which were soon correlated with those of the older 

 frictional electric machines. While the frictional 

 machine supplied isolated charges of small quantities 

 of electricity at a very high tension, showing their 

 existence on discharge by visible sparks, the new voltaic 

 battery gave a steady large current at a much lower 



