converting cast into malleable Iron. 261 
a considerable time I counted four, slowly, between each of 
these bubbles. I did not collect above three ounce measures 
of air, and this contained carbonic acid. It was past four 
o'clock when the apparatus ceased to be air-tight, and the fire 
had been kept as strong as possible. The iron was most com- 
pletely fused. There was a good deal of revived lead within 
the retort ; there were also many globules in the neck. Pro- 
bably some broken flint glass had been added to the usual ma- 
terials for crown glass ; I cannot otherwise account for the 
appearance of the lead here. In the last experiment the lead 
of the flint glass had been revived, 
EXPERIMENT V. 
Two ounces of the same iron, immediately upon being taken 
out of a retort, in which they had been kept, at a red heat, for 
about an hour and a half, and which were therefore as free 
from water as iron can easily be procured, were put into an 
earthen tube, unglazed, and closed at one end. This tube was 
disposed as in experiment 11, only the end of the glass tube 
was immersed in mercury, instead of water. You will not be 
surprised to hear that air did not now come over so soon as 
in any former instance. When the fire was raised to its full 
force, exactly the same amusing variety of appearances took 
place as in the last experiment. Under the pressure of half 
an inch of mercury, not a particle of air was discharged ; but 
the moment the pressure was diminished to a small fraction 
of an inch, the bubbles succeeded each other pretty quickly ; 
and so on repeatedly. Upon lowering the surface of the mer- 
cury, and pouring some water upon it, I received more than 
two ounce measures of air, which, by the test of lime-water, 
M m 
MDCCXCI I. 
