converting cast into malleable Iron. 263 
grains. Mr. Pelletier, if I remember right, found that na- 
tive plumbago, exposed to a fierce and long continued heat, 
lost 10 grains in 200. In the present experiment, its appear- 
ance was unaltered. Probably the loss was owing to moisture 
imbibed by the particles of coak, and to a small combustion 
by the air in the retort. 
It will, I think, be admitted, that these experiments abun- 
dantly confirm the inferences I had formerly drawn from ap- 
pearances by their nature less decisive. The real extrication 
of air, varying in its nature at various periods of the process, 
» 
seems to be placed beyond doubt. The experiments in glazed 
and glass vessels, were made with a view to exclude the possibi- 
lity of the supposition of the air entering through the pores. I 
think that Dr. Priestley, if he should repeat these experiments, 
and find that they have been accurately made, will, with his 
accustomed openness to conviction, abandon an opinion he has 
for some time entertained, and no longer consider water as es- 
sential to the constitution of elastic fluids. Several observa- 
tions might be made upon this point, and those which I have 
just noticed above ; but they will readily occur to persons 
conversant in chymistry, and it is not the object of the pub- 
lications of the Royal Society to teach the elements of science. 
I shall, therefore, confine myself to the unexpected and ano- 
malous appearances, and then attempt to draw a few useful 
inferences. 
1 . I was surprised at the extrication of inflammable air in 
such low degrees of heat. You have seen that cast iron, 
highly charged with charcoal (the phlogisto onustum of Berg- 
man) yields air at the temperature of melting lead. For un- 
doubtedly the blisters of lead, which lay upon the iron, are to 
Mm2 
