310 Experimental Inquiries respecting Heat and Vapor. 



bring the solid in one case, and the liquid in the other, into such con- 

 tiguity, as to restore in some degree the adhesion of the liquid or the 

 abrading power of the steel. The pressure may be applied directly 

 to the liquid when placed upon a metallic plate, by means of another 

 smooth metallic surface pressed immediately upon the drop of liquid. 

 Smart vigorous explosions may be thus produced, similar to the well 

 known cracking under a smith's hammer which has been dipped in 

 water and then applied to a hot bar of iron, or to the overheated face 

 of an anvil. 



The pressure of an elastic gas or vapor may, in like manner, be 

 employed to urge the liquid into contact with the metal ; and, it is ev- 

 ident, must become at every instant the more effectual, both as the 

 pressure is increased by the accumulating mass of steam, and as the 

 temperature is diminished towards the point of most rapid action. It 

 will be understood that the calculation formerly made respecting the 

 power which an overheated boiler of given dimensions could pro- 

 duce, was intended only to exhibit the amount of atmospheric steam. 



6. It becomes interesting to inquire whether any other liquid than 

 water is affected, in a similar manner, by the overheated metallic sur- 

 face. The trial soon convinced me that in regard to alcohol, at least, 

 the same general phenomena take place. It may at first appear sin- 

 gular, that a given portion of this liquid, (the boiling point of which 

 is at 174° Fahr.) should require for its evaporation a longer time 

 when laid upon a plate of iron at 400° or 500° than when poured 

 into the hand of the experimenter, the temperature of which is not 

 above 98°. Such however appears to be the fact. When one six- 

 teenth of an ounce of alcohol was laid upon the centre of an iron 

 basin, heated to at least 500°, the time of its final disappearance 

 was one hundred and forty five seconds j while an equal quantity of 

 the same spirit required but ninety seconds to evaporate it from the 

 palm of the hand. It is true, that in the latter case, the extent of 

 surface occupied by the spirit was unavoidably greater than that on 

 the iron. The liquid was diffused by capillary attraction, or perhaps 

 by its attraction for heat, over the whole surface of the palm, not- 

 withstanding the efforts to confine it to a single spot. At a tempera- 

 ture when the iron became barely red in the dark, the time of dis- 

 appearance was from one hundred and ten to one hundred and 

 twenty seconds. 



The next thing was to determine the time requisite to vaporize one 

 sixteenth of an ounce of alcohol, when the metal was at a temperature 



