. American engineer and railroad journal . impossible to introduce the compressing ma-chinery under the bell of the air-pump, he adopted the follow-ing ingenious method : The powdered graphite was formedinto a cake under a moderate pressure ; over its entire surfacewas then glued thin paper ; in one side was pierced a smallhole. The block was then introduced into the , and all the air and moisture removed. While stillin the vacuum the small hole was covered by an adhesive block was withdrawn and subjected to a regulated press-ure, and an artificial block of graphite
. American engineer and railroad journal . impossible to introduce the compressing ma-chinery under the bell of the air-pump, he adopted the follow-ing ingenious method : The powdered graphite was formedinto a cake under a moderate pressure ; over its entire surfacewas then glued thin paper ; in one side was pierced a smallhole. The block was then introduced into the , and all the air and moisture removed. While stillin the vacuum the small hole was covered by an adhesive block was withdrawn and subjected to a regulated press-ure, and an artificial block of graphite was produced. A num-ber of these blocks were then glued to a thin toard. Thelarger block this formed was cut into thin sheets, which werepassed to the fitter. This operative had before him a num-ber of grooved slips of cedar or juniper wood, prepared to formthe body of the pencil. Into the groove he inserted the edgeof one of the thin graphite sheets, which he then snapped offlevel with the surface, leaving a strip of lead in the THE GUILLAUME TIEJUSED ON THEfEASTERN RAILWAY OFJfFRANCE. lued (he other portionjof^thepencil to the considerable wealth to the owners, as the plumbago was foundin such a pure state and in such large pieces that it had mere-ly to be cut into long narrow bars by means of fine saws andbe immediately mounted in wooden cases. The loss, of course,was exceedingly great, and as small specimens were practi-cally useless, the surface lead was rapidly exhausted. Themine was pushed further, and certain curious restrictions wereput on its working. Once a year it was opened for a shorttime, and as much taken out as woidd suffice to meet the de-mand. But these restrictions were ; plumbago wasfound elsewhere, and it can now be imported from Ceylonand sold for less money than the Borrowdale lead costs. In-deed, it is doubtful if more than an insignificant quantity existsin Borrowdale. Next, as it had become evident that there wasa great demand for l
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
