Prof. Helmholtz on the Interaction of Natural Forces. 497 



by careful greasing from ignition through friction. Even lately 

 this property has been apjjlied on a large scale. In some fac- 

 toriesj where a surplus of water power is at hand^ this surplus is 

 applied to cause a strong iron plate to rotate swiftly upon another, 

 so that they become strongly heated by the friction. The heat 

 so obtained warms the room, and thus a stove without fuel 

 is provided. Now could not the heat generated by the plates 

 be applied to a small steam-engine, which in its turn should be 

 able to keep the rubbing plates in motion ? The perpetual 

 motion would thus be at length found. This question might be 

 asked, and could not be decided by the older mathematico- 

 mechanical investigations. I will remark beforehand, that the 

 general law which I will lay before you answers the question in 

 the negative. 



By a similar plan, however, a speculative American set some 

 time ago the industrial world of Europe in excitement. The mag- 

 neto-electric machines often made use of in the case of rheumatic 

 disorders are well known to the public. By imparting a swift 

 rotation to the magnet of such a machine we obtain powerful 

 currents of electricity. If those be conducted through water, 

 the latter will be reduced into its two components, oxygen and 

 hydrogen. By the combustion of hydrogen, water is again ge- 

 nerated. If this combustion takes place, not in atmospheric air, 

 of which oxygen only constitutes a fifth part, but in pure oxygen, 

 and if a bit of chalk be placed in the flame, the chalk will be 

 raised to a white heat, and give us the sun-like Drummond^s light. 

 At the same time the flame developes a considerable quantity of 

 heat. Our American proposed to utilize in this way the gases 

 obtained from electrolytic decomposition, and asserted, that by 

 the combustion a sufficient amount of heat was generated to keep 

 a small steam-engine in action, which again drove his magncto- 

 electi'ic machine, decomposed the water, and thus continually 

 prepared its own fuel. This would certainly have been the most 

 splendid of all discoveries ; a perpetual motion which, besides 

 the force that kept it going, generated light like the sun, and 

 warmed all around it. The matter was by no means badly cogi- 

 tated. Each ))ractical step in the affair was known to be possible; 

 but those which at that time were acquainted with the physical 

 investigations which bear upon this subject, could have affirmed, 

 on first hearing the report, that the matter was to be numbered 

 among the numerous stories of the fable-rich America; and 

 indeed a fable it remained. 



It is not necessary to multiply examples further. You will 

 infer from those given in what inmiediate connexion heat, elec- 

 tricity, magnetism, light, and chemical affinity, stand with me- 

 chanical forces. 



