1826.] Dr. Colquhoun on a new Form of Carbon. 7 



(not only as it seemed unique, but as the apparent extrication of 

 the pure metallic basis of that substance) was certainly the most 

 important phenomenon observed by me while superintending the 

 steelifying process, there occurred several other aggregations of 

 that substance during the progress of the same investigation, 

 which, upon various accounts, deserve to be noticed here. In 

 particular, their structure seemed so extremely analogous to that 

 of certain products which are formed in all manufactories of coal 

 gas, and as to the origin of which there is a schism among men 

 of science, that the advantage of comparing together the two 

 classes of products seemed to be too obvious to be passed over. 

 For the history of the one set of substances, so analogous, so 

 identical, indeed, as are these now alluded to, can scarcely fail 

 to throw considerable light on the history of the other, and to 

 assist in determining the question now at issue on this subject 

 among chemists. 



It is perhaps hardly necessary to mention that these aggrega- 

 tions of carbon were found by me within the steel chest or vessel 

 containing iron while under steelification by the absorption of 

 carbon precipitated from the gas in contact with it: the same 

 accumulation of precipitated carbon, which, in one or two rare 

 cases, was accompanied by the formation of filamentous carbon, 

 frequently producing those less uncommon and less striking 

 aggregations of which I am now to speak. 



It would be difficult to class the different specimens I have 

 met with by any well defined lines of distinction, and it would 

 be equally useless to attempt a minute description of each ; for 

 though the colour and aspect of the carbon vary from a dull 

 sooty appearance to that of a bright metallic lustre, though 

 different portions break with a very various fracture, and though 

 the substance is found sometimes in grains, sometimes in lumps, 

 and sometimes, as has been already noticed, in beautiful long 

 thin threads or hair, yet all these widely distinct kinds neverthe- 

 less shade away so much into one another, that it is often 

 extremely difficult to determine the boundary between the one 

 species and the other; and, in the same mass, most of the varie- 

 ties are found occasionally blended together. 



One of the most common appearances under which the carbon 

 thus presented itself was that of a quantity of finely divided 

 powder, bearing a strong resemblance to lamp-black, but, in 

 general, very considerably harder in the grain and denser, or of 

 greater specific gravity. Frequently, however, the particles of 

 carbon were not in this loose pulverulent state, but were found 

 collected into solid masses, possessing very different properties. 

 While some of these were soft and friable, others were of a hard 

 and compact structure. Some broke with a dull earthy frac- 

 ture, and crumbled readily away between the fingers ; while 

 Others with difficulty received any impression even from the 



