1823.] Scientific Intelligence. 311 



densation, it is difficult to ascertain, but every day's experience proves 

 it to be very considerable ; and, I believe, this, added to the other 

 obvious sources of heat in mines in a state of working, will be found 

 sufficient to account for their high temperature. (Trans. Wern. Soc. 

 vol. iv. part II. p. 466.) 



IV. On the Fusion of Charcoalf Graphite, Anthracite ^ and the Diamond. 

 By Professor Silliman. 



In our fourth volume, N. S.at p. 121, we gave an account of Prof. 

 Silliman *s experiments on the fusion of charcoal ; in vol. v. p. 314, 

 some remarks on the same subject by Mr. W. West, of Leeds, were 

 inserted ; and more recently, at p. 73 of the present volume, we gave 

 a notice respecting it by Prof. Griscom, of New York. Prof. Silliman 

 having extended his experiments to the more difficultly combustible car- 

 bonaceous substances, has published several articles concerning them 

 in the last number of his Journal, or that for May, the substance of 

 which we here present to the reader. 



The first article, p. 341, is a letter from Prof. S. to Dr. Hare, dated 

 March 26, 1823, in which, after referring to his former papers, he 

 proceeds to describe, in the following terms, the fusion of graphite by 

 means of Dr. Hare's deflagrator. 



*' From a piece of very fine and beautiful plumbago, from North 

 Carolina, I sawed small paralielopipeds, about one eighth of an inch 

 in diameter, and from three fourths of an inch to one inch and a quar- 

 ter in length ; these vvere sharpened at one end, and one of them was 

 employed to point one pole of the deflagrator, while the other was 

 terminated by prepared charcoal. Plumbago being, in its natural 

 state, a conductor, (although inferior to prepared charcoal,) a spark 

 was readily obtained, but, in no instance, of half the energj^ which 

 belongs to the instrument when in full activity, for the zinc coils were 

 much corroded, and some of them had failed and dropped out ; still 

 the influence was readily conveyed, through the remaining coils. As 

 my hopes of success, in the actual state of the instrument, were not 

 very sanguine, I was the more gratified to find a decided result in the 

 very first trial. To avoid repetitions I will generalise the results. The 

 best were obtained, when the plumbago was connected with the cop- 

 per, and prepared charcoal with the zinc pole. The spark was vivid, 

 and globules of melted plumbago could be discerned, even in the 

 midst of the ignition, forming and formed upon the edges of the 

 focus of heat. In this region also, there was a bright scintillation, 

 evidently owing to combustion, which went on where air had free 

 access, but was prevented by the vapour of carbon, which occupied 

 the highly luminous region of the focus, between the poles, and of 

 the direct route between them. Just on and beyond the confines of 

 the ignited portion of the plumbago, there v/as formed a belt of a 

 reddish brown colour, a quarter of an inch or more in diameter, which 

 \. appeared to be owing to the iron, remaining from the combustion 

 of the carbon of that part of the piece, and which, being now oxi- 

 dized to a maximum, assumed the usual colour of the peroxide of 

 that metal. 



** In variou5 trials, the globules were formed very abundantly on the 

 edge of the focus, and, in several instances, were studded around so 

 thickly, as to resemble a string of beads, of whjch the largest were of 



