on Evaporation. 
421 
11,35' 28,7 0,53 91,0 51 
.2,50 P.M. 28,72 0,60 86,75 54,15 
Here again, notwithstanding a constant maximum of eva- 
poration, moisture continued to diminish by the increase oi 
heat, as it does in air. 
The apparatus was left in that situation about four hours ; 
and the observers having left the room, this, and the ap- 
proaching evening, occasioned a sensible diminution in the 
heat ; whereby, as the sides of the vessel cooled before the in- 
closed space, the steam began to be decomposed against them, 
and they were found covered with dew and streaming water, 
by a real continuing distillation. The last cause of anomaly 
above mentioned is here conspicuous by its great effect ; for, 
during that distillation, and consequently though new quan- 
tities of steam ascended continually through the space, mois- 
ture was in it much less than in the former observations, as 
will be seen by the following, made before and after work- 
ing the pump. The thermometer could not be observed, on 
•account of the thickness of the dew on its side of the vessel. 
4,20' 27,35 — 76,0 
Worked the pump. 
4>35' 2 7’ 75 0,62 76,0 — 
The steam continued some time to decompose itself against 
the sides of the vessel, and moisture to remain in that state 
of diminution, till the heat communicated by the observers to 
the apparatus made the internal dew evaporate ; and when 
thereby the thermometer could be observed, the instruments 
were as follows. 
6,4/ 28,18 o ,6 96,0 52,75 
Here also is an instance of what I, have mentioned above, 
MDCCXCIJ. 3 I 
