=, € 
* 
312 Experimental Inquiries respecting Heat and Vapor. 
To place the matter beyond a doubt, the iron basin already men- 
tioned was used. When exposed to the white heat of a forge fire, 
a given weight (one eighth of an ounce) of water was evaporated in 
sixty seconds. At the bright red heat of an anthracite stove, eighty 
seconds were required to produce the same effect. When exposed 
on an open grate of anthracite, in such a manner as to maintain the 
centre only of the basin at a very faint red heat in the dark, the time 
was extended to three hundred and fifteen seconds. 
Another comparison, made upon portions of water of one sixteenth 
of an ounce each, gave the following results. On the metal, at the 
bright red heat of the stove, the water lay sixty six seconds; on the 
centre of the basin dull red, as before, in the dark, it continued one 
hundred and eighty three seconds ; while over a spirit lamp, the metal 
being constantly black and the temperature probably not above 600°, 
it remained two hundred and eighty six seconds. 
In all the above experiments, the heat was constantly supplied, and 
the temperature may be regarded as having been uniform during each 
trial. Hence, the opinion that repulsion increases with the tempera 
ture, appears not to be sustained. When the temperature has deci- 
dedly surpassed the point where contiguous attraction can take place, 
every elevation of temperature is attended with a corresponding dime 
nution of time required for evaporation. 
In order to illustrate more fully this branch of the subject, @ series 
of experiments was made with the iron basin, placed over a coa fire 
and supplied with doses of one sixteenth of an ounce of alcohol, sp: 
er. 854, (32.5° Baumé.) The first oe was made at @ 
temperature about 400° to 500°. Se 
The following was the succession. = ; 
Bapets tcc de Bap. 84 Se 
= pees gs ae 
- 145 &s 
The temperature of the metal continued to rise notwithstanding the 
application of the successive portions of spirit, and as the ume sl 
‘each experiment was obviously decreasing through an excess Of -, 
perature, the basin was removed from the fire and allowed to sta” 
for some time, until it was cooled below the point of minimum activity 
It was then again placed upon the fire, and when th 
liquid was placed upon it, exhibited symptoms of a slight — 
to attract the latter. The sixth experiment was made after sufficie 
time had elapsed again to permit a rise of temperature. 
