304 Experimental Inquiries respecting Heat and Vapor, 
Arr. VILL.—Experimental Inquiries respecting Heat and Vapor, 
with some practical applications ; by Water R. Jounson, Pro- 
fessor of Mechanics and Natural Philosophy in the Franklin Insti- 
tute, Philadelphia. 
Tux developement of the law of action between a heated surface 
and water of different temperatures, has been, in part, presented by 
preceding courses of experiments. 
To persons conversant with this subject it will readily occur, that 
the facts and principles connected with vaporization are highly im- 
portant to the arts, independently of their relation to the steam en- 
gine. ‘The numerous processes of manufactures, in which liquids 
are to be reduced by boiling, are often performed in a manner totally 
at variance with philosophy, as well as with economy. The manu- 
facture of salt by vaporization, for example, is an extensive and in- 
creasing branch of our national industry, and is generally carried on 
" with very little attention to the saving of fuel, by any of those devices 
and arrangements which the practical science of the present age 
might suggest. 
The chief points proposed to be examined at present, are—~ 
1. The temperature of most rapid vaporization under atmospheric 
pressure. 
2. The nature of the phenomena exhibited at that point, as well 
as immediately above and below it. 
3. Effects of lubricating the surface of the metal, of covering the 
surface of the water with a thin fibrous texture, and of thickening 
with a farinaceous substance. 
4. The influence of mechanical pressure in bringing the liquid 1 
contact with the metal and accelerating the vaporization. 
5. The action of hot metal on other liquids, particularly alcohol. 
6. Some opinions which have gained currency in regard to Tt 
temperature of repulsion, and the degree of rapidity with which heat 
may be imparted to liquids, will likewise require attention. 
i. To ascertain the temperature at which the most rapid action 
takes place, two methods have been employed. The first was by 
using a basin of wrought iron, having at the bottom a small quantity 
of mercury, into which the bulb of a thermometer was plunge 
Upon the surface of the iron, near the mercury, small measured #2 
tions of water were successively deposited, while the basin Was 
