72 Mr. Faraday on the Limits of Vaporisation. 



and pass it forward ; only the facility with which the carrying 

 agent is condensed when it consists of steam, allows of the 

 condensation of every particle of the essential oil vapour, 

 whereas the permanency of the elastic state of the air would 

 cause it to retain a large proportion of the vapour of the oil 

 when cold, and consequently a diminished result would be 

 obtained. 



There are, nevertheless, some appearances which seem to 

 favour the idea that occasionally water favours vaporisation 

 beyond what air, equal to the bulk of the vapour of the water, 

 would do in the manner referred to above ; and it was to ascer- 

 tain whether substances which, from a consideration of the 

 general reasoning already referred to, and the high tempera- 

 ture at which they sensibly volatilized, might be considered as 

 fixed at common temperatures, could have any sensible degree 

 of volatility, in conjunction with water or its vapour, conferred 

 upon them at ordinary temperature. It is well known that a 

 theory of meteoric stones has been founded on the supposition 

 that the earthy and metallic matter found in them had been 

 raised in vapour from similar matter upon the earth's surface ; 

 which vapours, though extremely attenuated and dilute at first, 

 gradually accumulated, and by some natural operation in the 

 upper regions of the atmosphere became condensed, forming 

 those extraordinary masses of matter which occasionally fall to 

 us from above. The theory has in its favour the remarkable 

 circumstance, that, notwithstanding many substances occur in 

 meteoric stones and iron, yet there is none but what also occur 

 on this our earth * ; and it also has a right to the favouring 

 action of water, if there be such an action ; because vaporisa- 

 tion is one of the most important, continual, and extensive 

 operations that goes on between the surface of the globe and 

 the atmosphere around it. 



In September, 1826, several stoppered bottles were made 

 perfectly clean, and several wide tubes close at one extremity, 

 so as to form smaller vessels capable of being placed within 



* This very striking circumstance does not prove that aerolites in any way 

 originate from our planet j but then, if we could by other arguments deduce that 

 they were extraneous, it would lead to the conclusion that the substances which 

 have been used in the construction of this our globe, are the same with those 

 which have been used extensively elsewhere in the material creation. 



