128
Class 1.— MINING- AND MINERAL PRODUCTS.South Side—Areas S. 1 to S. 27.
[United
62 Dyer, William Bunt, Mold — Proprietor.
White lead ore, carbonate of lead ore, from Jamaica
mine. Assay, 60 per cent, for lead, and four ounces ofsilver per ton of lead.
Blue lead (galena) and sulphuret of lead ores fromJamaica mine. Produce 80 per cent, lead and fourounces silver per ton of lead. It is used by potters forthe purpose of smoothing earthenware glaze.
63 Cairns , J., jun., 96 Charlotte Street, Manchester —
Producer.
Carbonate of barytes, with specimens of lead ore, fromAnglezark Moors/near Chorley, Lancashire.
64 Brookman & Langdon, 28 Great Bussell Street —
Proprietors.
Specimens of black lead from Cumberland, in the rawstate, and as hardened for use. Specimens of otherminerals.
[The Cumberland graphite is obtained from a large andvery irregular vein cutting through the green slate andporphyry; and the mineral occurs in large lumps, foundhere and there expanding and thinning out with no appa-rent order. About 50 years ago, one of the largest massesever discovered was suddenly met with, and yieldedabout 70,000 lbs. of the purer kind of black lead. Sincethen there has been nothing found of any value. Themines are near the head of Borrowdale, the entrancebeing about 1,000 feet above the sea, and as much belowthe summit of the mountain.—D. T. A.]
65 Brockeuon, W., 29 Devonshire Street, Queen Squai'e
—Patentee and Manufacturer.
Native plumbago:—Samples from the mines of Borrow-dale in Cumberland, fine and crude: from Ceylon , Davis’Straits, Spain, Bohemia (called Mexican), Greenland ,California, France (Poligny): nodules from India , See.
Samples of Cumberland black lead, prepared for con-densing into blocks by patent process.
Specimens in powder, purified from grit, and in finepowder, ready for condensing, which has passed throughapertures -Am fR °f an inch in diameter.
Blocks which have been condensed by a pressure of5,000 tons.
Slices of the blocks for pencil-makers ; points forMordan’s ever-pointed pencils; cedar pencils, by variousmakers, of Brockedon ’s patent Cumberland lead.
Blocks made of Ceylon and other plumbagos, &c.
The plumbagos exhibited in their natural state, are—Three very fine samples of the old black-lead, formerlyfound in Cumberland. The only native plumbago whichcould be cut into slices, and used in its natural state; theminers have long failed to supply such specimens. Twosamples of Cumberland lead, containing too much grit tobe used without purification. Samples of plumbago fromCeylon , crystalline and fibrous: this is the purest plum-bago known, being 98 - 55 pure carbon; but it is toofragile for use in cedar. Two samples from Davis’sStraits and Greenland. One from California . Othersfrom Spain and Bohemia (called Mexican ), of these twothe common pencils are made, when hardened by sul-phur. From none of these can a fine pencil be made, butthe Cumberland.
The manufactured blocks are from the second varietyof the Cumberland, freed from grit, and reduced to animpalpable powder, of which a quantity is shown toform one of the blocks. From this powder the air isexhausted, when it is condensed in a dry state by anenormous pressure, which consolidates a mass weighingseven ounces under a force, in two blows, with a force of5,000 tons, leaving it as compact as the natural; and fromthese blocks slices are cut, as shown: these are inserted inchannels in the cedar. It is also cut into the lengths ofthe block as square threads; these are rounded, then cutto the proper lengths for the ever-pointed pencils.
For the process by which the Cumberland lead can
be freed from grit, and then solidified, the exhibitorobtained a patent, and pencil manufacturers use it onlyfor their finest drawing pencils.
[Graphite or Plumbago, a form of carbon commonlycalled black-lead, and sometimes, but incorrectly, regardedas a carburet of iron, is a well-known soft mineral, crys-tallized in small hexagonal plates of laminated structure,infusible, burning with great difficulty under the blowpipe;consisting of from 85 to 98’55 per cent, of carbon, andhaving a specific gravity of 2’09 to 2*25; the purest beingthe lightest. It is found in metamorphic, generally inschistose, rocks, of various geological age, in masses orveins parallel to the lamination or stratification. The pureand valuable kinds are very rare, and have been ob-tained almost exclusively from the localities mentionedabove. The variety from Ceylon is remarkably pure butsoft; that from Greenland is also pure, but very hard.The latter, according to an analysis recently made byT. H. Henry, Esq., yields carbon 96*6, ash 3*4; but doesnot seem adapted for extensive use in pencil-making,owing to its hardness and paleness. It appears that thepresence of a certain quantity of iron is favourable for itsuse in the arts.
The method by which Mr. Brockedon has renderedseveral of the softer and less compact graphites available,and has also brought into use the fragments formerly toosmall for pencils, has been successfully applied to othermaterials for various useful purposes.—D. T. A.]
66 Reeves & Sons, 113 Cheapside —Inventors
and Manufacturers.
Cumberland lead and cedar wood, in the different formsin which they are used in the manufacture of drawingpencils.
67 Adair, R., Manyport —Manufacturer.
Various materials used in black-lead pencil making;
with specimens of pencil manufacture, in its differentstages.
The cedar used is imported into London and Liverpoolchiefly from South America . The foreign plumbago, ofwhich common pencils are manufactured, is importedfrom Germany, the East Indies, Spain, and Mexico .The Cumberland black-lead is found only in Borrowdale,and is used only for the best pencils.
68 Wolff & Son, Church Street, Spitalfields —
Manufacturers.
A specimen of pure Cumberland lead, without grit, asproduced from the mines at Borrowdale. Block of thesame compressed. Specimens of prepared and compressedCumberland lead.
[The Cumberland mines having failed to produce acontinual supply of the pure plumbago, or black lead,for the use of artists, &c., the exhibitors are enabled, bytheir process of cleansing and compressing the crude orgritty lead, to produce solid blocks of pure plumbagoequal to the finest quality originally supplied from themines.]
Specimen of Ceylon black lead. East India , as pro-duced from the mine. Block of Ceylon lead, preparedand compressed.
Specimen of Malaga black lead (Spain ), as producedfrom the mines. Block of Malaga lead, prepared andcompressed.
[Plumbago, or graphite, improperly called black lead,is a carburet of iron : the best quality of this is used forartistic purposes ; the inferior is employed in the manu-facture of crucibles, or chemical furnaces, as it stands ahigh temperature. It is adulterated with lamp black,sometimes to the amount of 60 per cent., when sold fordomestic purposes.—R. H.]