168 Experiments on Anthracite, Plumbago, &c. 
little change when it was not used; although the heat was, in 
this ase, of | nger conti uance. Matter similar to the im- 
p ri es discov red in the substances used, was detected in 
tiem. 
F these acts it would appear, that the globules pro- 
duce’ om the combustible substances operated upon, did 
not arise from the fusion of their carbon, since they can 
otherwise be accounted for; particularly as no experiment 
has been made wh'ch unequivocally leads to that conclusion. 
The experiment upon which Professor Silliman relies, as a 
proof of the globules being fused carbon, is one which is not 
satisfactory to me ; if it had been, it would have given me 
great pleasure ; for no one, f trust, feels more interested in 
the scientific prosperity of his country than I do; and if 
Professor Silliman were right, it would indeed be a triumph 
for America. 
The experiment just alluded to, (see vol. vi. p. 347, 
Journal of Science,) is the heating some of the coloured 
globules in oxygen gas by the solar rays, with a lens. The 
following is an extract from the papers. 
“To detach any portion of unmelted Plumbago which 
might adhere to them, I carefuily rubbed them between my 
thumb and finger, in the palm of my hand. Although they 
were in the focus for nearly half an hour, they did not melt, 
disappear, or alter their form; it appeared, however, on ex- 
amining the gas, that they had given up a part of their sub- 
stance to the oxygen, for carbonic acid was formed which 
gave a decided precipitate with lime-water,” 
That this experiment is equivoca appears certain, as par- 
ticles of the support might bave been attached to the 
lobules ; for. from my own observations, I found that ina 
great number of instances, some of the white globules at the 
point of junction with their support, had small dark particles 
attached to them, and when the surface from which they 
were detached was magnetic, they were attracted by the 
magnet when it was presented to those parts; I could not 
disengage those particles by rubbing the globules with my 
fingers One against another. It is very evident that. as the 
globules underwent no change, (unless a reduction of 
yolume, which is not mentioned) as the description clearly 
shows, the carbonic acid obtained. might have been produced 
by the combustion of portions of the support adhermg to 
them externally, and penetrating them to a certain extent. 
