May 1, 1864.] THE TECHNOLOGIST. 



THE PATENT PLUMBAGO CRUCIBLE COMPANY. 467 



The total quantity of graphite exported from Ceylon in 1862 was 

 40,895 cwt., of which no less than 34,7i!0 cwt. was shipped to Great 

 Britain. The Customs' returns for last year have not reached us. "We 

 do not wish it to he understood that the Patent Plumbago Crucible Com- 

 pany use up all the Ceylon graphite brought to the United Kingdom, 

 but it is well-known that they are the principal consumers. We must 

 now take leave of chemistry and statistics, and see what there is to be 

 seen at the Black Potteries. 



We commence our tour of inspection at the Receiving Stores, where 

 we are shown the stock of raw material, which comprises at present 

 about 2,000 casks of graphite, each one holding from four to five cwt. 

 The heads of a couple of casks are broken open, in order that we may 

 compare the hard iron-grey fragments of the Ceylon graphite with the 

 black, dull, friable lumps of the German variety. A piece of the latter 

 pressed between the finger and thumb feels pleasantly soft, and flattens 

 readily into a lustrous cake. From the stores we pass to the engine- 

 house, to take a peep at the prime mover of the machinery employed on 

 the factory. One horizontal engine of 25-horse power serves to do all 

 the work that does not require skilled hands. 



The grinding-room contains several mills of different construction for 

 grinding and mixing the materials of which the crucibles are formed. In 

 one corner we see two huge stones chasing one another round a shaft, 

 and pitilessly crashing the hard lumps of dried clay that are thrown in 

 their path. Here we see a powerful mil l for grinding the graphite, 

 and an ordinary pug-mill for incorporating the graphite with the 

 clays. The noise made by these machines is almost unbearable, but 

 it is not only the noise we have to put up with. A brisk rattle is 

 maintained by a number of workmen, who are occupied in sorting the 

 pieces of graphite into different sizes and qualities by the aid of me- 

 tallic sieves. When the graphite is reduced to powder, it is conveyed 

 to the upper floor by an endless band-lift, and sifted by a contrivance 

 similar to an ordinary flour-dressing machine. One of these machines 

 is provided with a silk-gauze drum of remarkable fineness, and is 

 reserved for the preparation of plumbago for anti-friction purposes. 



Following the graphite to the upper floor, we enter the niLxing-room, 

 where the most important operation in the crucible manufacture is per- 

 formed. A number of large bins, each containing a distinct variety of 

 clay in powder, or a certain quality of plumbago, are ranged round the 

 room. Upon the proportions of these several ingredients taken to form 

 the mixture, or " metal " as it is technically termed, the quality of the 

 crucibles depends. The actual proportions of Stourbridge and other 

 clays used are of course kept secret. The ground graphite having been 

 mixed with the clays, the whole is wetted with a sufficient quantity of 

 water, and allowed to soak for some time. Having been " pugged " in 

 the mill, the tempered " metal" is formed into blocks, and then placed 

 in a store-room, where it is allowed to remain for several weeks. 



