relating to Air and IV titer, 2$ 3 
This calx of iron, I then concluded, was by no means what 
1 had before taken it to be, viz. a pure calx or flag, but either 
the calx, or the iron itfelf, fa tu rated with pure air. This cal- 
eiform fub fiance 1 found, by various experiments, to be the 
fame thing with this fcales that fly from iron when it is made 
red-hot, or the fubflance into which it runs in a very intenfe 
heat, in an open fire. 
'Concluding from the preceding experiment, that iron, fuffi- 
ciently heated, was capable of faturating itfelf with pure air, 
extradled from the mafs of the atmofphere, I then proceeded to 
anclt it with the heat of a burning lens in the open air ; and I 
prefeutly found, that perfect iron was eaflly filled in this way, 
-and continued in this fufion a certain time, exhibiting the ap- 
pearance of boiling or throwing out air, whereas it was on the 
contrary imbibing air; and when it was faturated the fufion 
ceafed, -and the heat of my lens could not make any farther 
dmpreflion upon it. When this was the cafe, I always found 
that it had gained weight in the proportion of pf to 24, which 
4 s very nearly one-third of its original weight. The fame was 
•the eiTefl when 1 melted Jleel in the fame circumftances, and 
alfo every kind of iron on which the experiment could be tried. 
But I have feme reafen to think, that with a greater degree of 
heat than 1 could apply, the iron might have been kept in a 
■fee of fufion fomewhat longer, and by that means have im- 
bibed more air, even more than one-third of its original 
weight. 
There was a peculiar circumfiance attending the melting of 
rCtiJl iron with a burning lens, which made it impoflible to afcer- 
tain the addition that was made to its weight, and at the fame 
time afforded an amazing fpedtacle ; for the moment that any 
quantity of it was melted, and gathered into a -round ball, it begun 
O02 to 
