222 



JOURNAL, R.A.S. (CEYLON). 



[Vol. IX. 



pots used in most countries being made of clay and sand; but the 

 late Mr. Joseph Dixon, the founder of our house, in 1827 made 

 crucibles by using the plumbago found in the State of New 

 Hampshire, of a quality so far superior to the Dutch black lead 

 pots that he took the market from the first. He afterwards saw 

 specimens that had been brought from Ceylon as curiosities by 

 Captains in the India trade ; and finding them so much better 

 than the New Hampshire plumbago, he procured a shipment, 

 being the first importation of Ceylon plumbago to the United 

 States. For crucibles the pure lumps known as 4 prime lumps' 

 only should be used, ground to a fineness that leaves the particles 

 bright and glistening when held to the light, but not so fine as to 

 destroy this appearance. It is then mixed with clay, and the 

 best known for that purpose is found at Mayence, comes down 

 the Rhine, and is shipped to this country from Rotterdam. A 

 small amount of finely-pulverized charcoal should be added to 

 render the crucible porous. As little clay should be used as will 

 suffice to hold the plumbago together, the object in using the 

 clay being only to cement the particles of plumbago. After a 

 thorough mixture, the crucibles are turned into the desired shape, 

 much the same as potteryware ; they are then dried in a kiln 

 like pottery. In use the crucibles should be placed in the fire, 

 and not on it. The fire should surround the crucible to the very 

 top. If used with a blast, the blast should not strike the crucible 

 direct, but there should be coal for the blast to strike against. 

 The crucible should be kept in a dry place, the least dampness 

 being fatal. If they are well made, no annealing is needed, the 

 object of annealing being only to complete the shrinkage that 

 should be fully accomplished in the 6 burning' by the crucible- 

 maker. To provide against slight dampness, however, it is well, 

 when possible, to use the crucible for the first time in a new fire, 

 placing the crucible in the furnace at the time of lighting the fire, 

 so that it heats up gradually with its surroundings. After the 

 first time even this precaution is unnecessary. For melting brass, 

 copper, gold, silver, or alloys of metals, a Dixon Plumbago 

 Crucible should run from twenty to forty meltings according to 

 the fuel, draught, care, or other circumstances. I have known 

 them used seventy and even eighty times, with a natural draught 

 and great care. For melting steel, they will run from four to six 

 times. They can be made to run longer by care and a system of 

 cleaning the slag from the surface after each melting, and coating 

 the crucible with a mixture consisting of fire clay, plumbago, 

 charcoal, and silica 5 pure fine quartz sand being, in roy judgment. 



