306 Hon. C. A. Parsons on Carbon at High 



The specimens were treated with solvents, and there ap- 

 peared no indication of the surrounding substance having 

 penetrated the rod ; the carbon was undoubtedly consolidated 

 by 30 per cent. 



In some cases, when the material surrounding the rod was 

 alumina saturated with oil, soft crystals of graphite exuded 

 from specimens that had been kept for some weeks. 



No. 2. Pure hydrated alumina, carbonate and oxide of 

 magnesia, and lime all rapidly destroyed the carbon rod, by 

 combining with it, the hydrated alumina forming large 

 volumes of gas of which it appeared to be a constituent. On 

 account of the great diminution of bulk, no analysis was made; 

 the gas issued from the mould explosively at from 10 to 

 12 tons per square inch. The alumina was found in a crys- 

 talline crust, like sugar, around where the rod had been. 

 Hardness that of corundum, almost translucent. 



No. 3. The following is the most interesting experiment of 

 the series : — 



On the bottom of the mould was a layer of slaked lime 

 about J inch thick, over this silver sand 2 inches, then another 

 layer of lime of the same thickness as the former, finally a 

 layer of coke-dust, and then the plunger. With a pressure of 

 from 5 to 30 tons per square inch in the mould, and the 

 carbon of from £ to -^ inch diameter, currents of from 200 to 

 300 amperes were passed. 



In from 10 to 30 minutes the current was generally inter- 

 rupted by the breaking or fusing of the rod, or by the action 

 of the lime in dissolving it at the top or bottom. On opening 

 the mould when it had cooled a little, the silica usually 

 appeared to have melted to an egg-shaped mass, and mixed 

 somewhat at the ends with the lime ; the surface of the carbon 

 appeared acted on, and sometimes pitted and crystalline in 

 places ; silica adhered to the surface, and beneath, when 

 viewed under the microscope, appeared a globular cauliflower- 

 like formation of a yellowish colour, resembling some speci- 

 mens of "bort"*. 



After several days' immersion in concentrated hydrofluoric 

 acid, this formation remained partly adherent to the carbon ; 

 on the surface of the carbon was a layer or skin about -^ of 

 an inch thick of great hardness, on the outside grey, the 

 fracture greyer than the carbon, but having a shining coke- 

 like appearance under the microscope. 



The powder scraped off the surface of the rod has great 

 hardness, and will cut rock crystal when applied with a piece 



* The bort-like powder is not acted on by hydrofluoric and nitric acids 

 mixed. 



