124 ANNUAL OF SCIENTIFIC DISCOVERY. 



In the mightiest of our machines, the steain engine, it is a strongly com- 

 pressed aeriform body, water vapor, which, by its effort to expand, sets the 

 machine in motion. Here also we do not condense the steam by means of 

 an external mechanical force, but by communicating heat to a mass of water 

 in a closed boiler, we change this water into steam, which, in consequence 

 of the limits of the space, is developed under strong pressure. In this case, 

 therefore, it is the heat communicated which generates the mechanical force. 

 The heat thus necessary for the machine we might obtain in many ways ; 

 the ordinary method is to procure it from the combustion of coal. 



Combustion is a chemical process. A particular constituent of our at- 

 mosphere, oxygen, possesses a strong force of attraction, or, as it is named 

 in chemistry, a strong affinity for the constituents of the combustible body, 

 which affinity, however, in most cases, can only exert itself at high tempera- 

 tures. As soon as a portion of the combustible body, for example the coal, 

 is sufficiently heated, the carbon unites itself with great violence to the oxy- 

 gen of the atmosphere and forms a peculiar gas, carbonic acid, the same 

 which we see foaming from beer and champagne. By this combination, light 

 and heat are generated ; heat is generally developed by any combination of 

 two bodies of strong affinity for each other ; and when the heat is intense 

 enough, light appears. Hence, in the steam engine, it is chemical processes 

 and chemical forces which produce the astonishing work of these machines. 

 In like manner the combustion of gunpowder is a chemical process, which, 

 in the barrel of the gun, communicates living force to the bullet. 



While now the steam engine develops for us mechanical work out of 

 heat, we can conversely generate heat by mechanical forces. A skilful 

 blacksmith can render an iron wedge red hot by hammering. The axles of 

 our carriages must be protected, by careful greasing, from ignition through 

 friction. Even lately this property has been applied on a large scale. In some 

 factories, 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 steain 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, before- 

 hand, 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 magneto-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 hydro- 

 gen. By the combustion of hydrogen, water is again generated. If this 

 combustion takes place, not in atmospheric air, of which oxygen only con- 

 stitutes a fifth part, but in pure oxygen, and if a bit of chalk be placed in 



