110 Mr. L. Vamixem on Anthracite, Plumbago, S^c. [Feb. 



upon which Prof. 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, I 

 trust, feels more interested in the scientific prosperity of his 

 country than I do ; and if Prof. SiUiman 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 carefully 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 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 certain, as particles 

 of the support might have been attached to the globules ; for, 

 from my own observations, I found that in a 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 mag- 

 netic, 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 pro- 

 duced by the combustion of portions of the support 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 origin, 

 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. 



Prof. 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 pre- 

 sence 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. 



1 was sorry to observe that Professor Silliman in his reply to 



