420 Dr. Schafhaeutl on the Different Species of 



gas takes place, and on cooling, the bottom of this slag, not 

 only that part which has touched the coal, but also where it 

 came in contact with the gas evolved, is found to be covered 

 with a thinner or thicker pellicle of graphite or plumbago, 

 which possesses all the properties, both externally and che- 

 mically, of the kish or graphite, which separates itself from 

 gray kishy iron during its refrigeration. 



The larger fragments of the coal enveloped by the liquid 

 slag are either converted into a very light black spongy body, 

 retaining the outlines of the coal fragment, and perfectly en- 

 veloped with an interlayer of a silvery rugose pellicle of gra-^ 

 pliite ; or the coal itself is converted into a metallic shining 

 body, perfectly resembling coke, in which case no grapliite 

 pellicle is to be found. This last circumstance appears only 

 to occur when the silicate is at the highest degree of tem- 

 perature. For the generation of this kind of artificial gra- 

 phite, a very liquid silicate is invariably necessary, as well as 

 highly bituminous coal, the temperature ranging between 1500 

 and 2000 degrees Fahr., and probably much lower, as I shall 

 presently show. I saw sometime since in the iron works of 

 Messrs. Solly and Sons, near Dudley, thin streams or layers 

 of slag running out of the flue hole of a balling or reheating 

 furnace, and moving slowly towards an already cooler cake- 

 like mass of the same slag. Just before the running slag came 

 in contact with the other already stiff" one, I put some coal- 

 dust in its way, over which the wave ran, immediately over- 

 lapping the already cooler ore. The heat of the liquid slag, 

 measured by the expansion of platinum, was 1500° Fahr. The 

 usual gases escaped as a yellowish brown smoke, and on their 

 cooling, on inspecting the two slightly adhering pieces of slag, 

 I found the lower one, just over the point of connexion, where 

 the smoke escaped, surrounded by a lively orange-red border, 

 probably an oxide of iron, which could not be removed from the 

 surface. By tracing this, and separating carefully the pieces 

 from each other, I found the lower cake of slag covered on 

 its rounded edges with the before-mentioned grap/nte pellicle, 

 forming tiear the orange-coloured borders one ijiseparahle and 

 continuous body with the slag itself but getting gradually 

 looser as it descended towards the bottom of the cake. I cut the 

 pellicle with a knife across from the bottom of the cake, and it 

 rolled itself immediately up towards the top, where it im- 

 mersed itself into the mass of the slag, so that even with a 

 magnifying glass it could not be distinguished from the slag 

 itself. The pellicle was near the bottom about the thickness 

 of common letter-paper, but gradually becoming thinner, until 

 its trace became lost on the surface. The surface of the slag, 



