188 Proceedings of the 



spontaneously, as accessibly, and at the same temperature as water, 

 even then water would be the most economical source of power. 



From this it appears, that the temperature at which a liquid 

 vaporizes, and the quantity of latent heat absorbed in the process, 

 form no criterion of its eligibility for the production of mechanical 

 force ; and that, therefore, there is no reason at present to expect 

 that power can be obtained from liquid carbonic acid gas, or any 

 other of the gases liquefied by Mr. Faraday, more cheaply than from 

 water, merely because of the low temperatures at which they become 

 highly elastic. Analogy, it is evident, would lead to a conclusion 

 exactly the reverse, and would induce an expectation that the 

 vapour of mercury, or even of metals vaporizing at a much higher 

 temperature, would furnish the most economical motive power. 



Mr. Ainger then described a mode of increasing almost indefi- 

 nitely the power, or, in other words, of decreasing almost indefinitely 

 the expense of the steam-engine, which has not hitherto been suggest- 

 ed, and which appears to require for its realization, only the discovery 

 of a succession of hquids, whose boiling points should differ about 

 100° of Fahrenheit; whose nature should not alter by repeated distil- 

 lation ; and which should exert no injurious action on the substances 

 composing the machinery of the steam-engine. The difficulty of 

 finding such a series of liquids is probably insuperable ; if it were 

 not so, there can be little doubt that the cost of steam power would 

 be susceptible of an immense reduction. If, for instance, a suc- 

 cession of liquids could be obtained, whose boiling points were 

 612°, 512°, 412°, 312°, and 212^ and if the furnace were applied 

 to the first, and its vapour were employed to work a condensing 

 engine, it is clear that the vapour which was condensed at 612°, 

 could be made to evaporate the second liquid, by condensing the 

 first on the surface of the vessel containing the second, the vapour 

 of which would, in its turn, work a steam-engine. The condensa- 

 tion of the second vapour at 512° might, in like manner, evaporate 

 the third liquid which boils at 412°, and so on, till the water which 

 boils at 212° was evaporated, and which might be condensed by 

 injection in the usual way. 



It may perhaps be thought that a cooling surface at 512° will 

 not sufficiently reduce the tension of a vapour at 612°, to leave any 

 effectual difference between the pressures on the two sides of the 

 piston; but it must be recollected, that a depression of 100° re- 

 duces the elastic force of a vapour produced at 612°, as much as of 

 one produced at 212°. The elastic force of common steam at 



