071 Anthracite, Plumbago, 8fc. 167 



and finger, in the palm of my hand. Ahhough they were in 

 the focus for neai'ly half an hour, they did not melt, diappear, 

 or alter their form ; it appeared, however, on examining the 

 gas, that they had given up a part of their substance to the 

 oxygen, for carbonic acid was formed which gave a decided 

 precipitate with lime-water." 



That this experiment is equivocal appears cei'tain, as parti- 

 cles of the support might have been attached to the globules ; 

 for, from my own observations, I found that in a great num- 

 ber 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 Trom 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 against one another. 

 It is very evident that, as the globules underwent no change 

 (unless a reduction of volume, which is not mentioned), as the 

 description clearly shows, the carbonic acid obtained might 

 have been produced by the combustion of portions of the sup- 

 port adhering to them externally, and penetrating them to a 

 certain extent. 



In the experiment detailed in vol. v. p. 363, of the same 

 Journal, the carbonic acid found probably had a similar ori- 

 gin^ and the disappearance of the globules may have been 

 owing to their incorporating themselves with the piece of brick 

 upon which they were placed, as the brick was vitrified at the 

 point where they were placed. 



Professor Silliman seems disposed to lay great stress on the 

 loss in my examination of the globule sent by Dr. Macneven. 

 I thought I had well accounted for it, as the particle was 

 small, action violent, and I merely wished to show chemically 

 the presence of iron. I could not for one moment entertain 

 the idea that carbon existed in it, in any notable proportion ; 

 for I know of no combination of iron and carbon, at common 

 temperature, which could give a product possessed of the 

 malleability and toughness which the globule possessed. 



I was sorry to observe that Professor Silliman in his reply 

 to my paper seems offended that I did not notice his commu- 

 nications upon the subject of these globules, particularly as the 

 discovery was his, and was justly entitled to such consideration. 

 My silence certainly appeared uncourtly; but it was not owing 

 to ignorance of his labours, or a want of rcgaid to him per- 

 sonally, or as a chemist; Professor Silliman's merit is too well 

 known to be affected by me. 



XXIII. On 



