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- 
ideut, 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 atmospherte steam. 
5. 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 om 
above 98°, Such however appears to be the fact. When one xt 
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; 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 om 
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 toa single spot. Ata 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 on° 
sixteenth of an ounce of alcohol, when the metal was at a temperatur’ 
