No. 31.— 1885.] 



PLUMBAGO. 



227 



Finally, Mr. Cleveland gives the following information : — 

 "For Blast Furnaces.—- Plumbago thrown into the blowing 

 cylinders, if adulterated with coal dust, will be worse than 

 nothing. It should be pure and very fine, so that each particle 

 that strikes the side of the cylinder assists in polishing the sur- 

 face. The German black lead is of no value, because as many 

 particles of the clay character will stick to the iron as there will 

 be particles of the black lead character to lubricate the iron 

 and render it smooth. 



C5 Refractory Mixtures. — For tweers, pointing-up furnaces, &c, 

 take 6 prime lump' Ceylon plumbago, pulverized to scales as 

 directed for crucibles. Then mix equal parts of Dutch pipe- clay, 

 fireclay, half the quantity (by measure, not weight) of charcoal, and 

 the same hal f quantity of silica (pure quartz sand ground fine being 

 the best) ; to this mixture add as much of the plumbago as possi- 

 ble and leave the mass thin enough to work. It should be made 

 just thin enough with water, so that it will run rather sluggishly. 

 Plumbago for polishing powder should be of the very best quality ? 

 finely pulverized. The German black lead is sometimes used, but 

 is not economical for the powder maker, and for high-priced 

 powder is useless. Shot is polished with plumbago, and it should 

 be absolutely pure, pulverized to the finest grade from Ceylon 

 'prime lump.'" 



Mr. Cleveland's very interesting and valuable notices of 

 the American Crucible Company, and their varied manu- 

 factures of plumbago, is supplemented and brought down 

 to so late a date as 1883 by the writer (Mr. John A. Walker) 

 of an article on Plumbago in a volume on the " Mineral 

 Resources of the United States," prepared by the National 

 Geological Survey Department, and supplied to our Library 

 by the Smithsonian Institute, to which my attention 

 was attracted by our Honorary Secretary, when he asked 

 me to write this paper. In the summary prefixed to 

 this volume it is stated that the amount of graphite 

 mined in the States in 1882 was 425,000 lb., worth crude 

 at the point of production 34,000 dollars, equivalent 

 to about Rs. 70,000. During the first six months of 1883 

 the production was estimated at 262,500 lb., worth 21,000 

 dollars. From Mr. Walker's detailed account we learn that 

 graphite is, as a mineral, widely distributed in the United 

 States ; as an ore it is found in but few places in sufficient 



