Proceeding's of the Polytechnic Association. 871 



detracting from its writing qualities ; glue, isinglaes, gum arable, and 

 other gums were applied in vain ; metallic antimony succeeded but 

 partially; sulphur came nearest to perfection, but produced too 

 brittle a compound, and the marks made with it remained faint. 



In 1795, an ' important discovery was made in France, which 

 proved a great success, and has become the basis of the present 

 manufacture of pencils. It was the admixture of tine clay with the 

 purified graphite ; it not only restored to the graphite the necessary 

 consistency, without materially diminishing its writing qualities, but 

 also any degree of hardness or softness, a result that could not be 

 obtained from the pure Borrowdale. This process is now generally 

 practiced in the following manner : 



The graphite is crushed, washed, and' floated in large vats, and the 

 clay undergoes the same operation. The floated materials are dried 

 in pans at low temperature, and then mixed together in the requisite 

 proportions. The combined substances are now ground in iron mills 

 as fine as possible, and then kneaded by skillful hands like dough, 

 and put in a cast-iron cylinder, from which it is forced by a 

 severe but low pressure through a small hole at" the bottom, 

 through which it passes in the shape of a continuous thread, 

 coiling itself like a rope on a board below. This . continuous 

 thread is straightened out into the requisite lengths and laid close 

 together in layers, kept in their places and prevented from warping 

 by a slight pressure. It is then dried at a moderate temperature, and 

 when properly dry, packed in crucibles, hermetically sealed, and 

 submitted to high heat in ovens of a peculiar construction. ' The 

 graphite is now finished. The most important operation of trying 

 its qualities is now undertaken ; and as the entire reputation of' the 

 maker of lead pencils depends upon it, it requires a very skillful hand. 

 The approved black lead is now ready for the. wood, which is mostly 

 cedar. No other has been found to answer.- as. well. This cedar is 

 imported from Florida; it is cut up in smalLstripsiand grooved out, 

 and the lead glued in, and another strip glued over.it. .The pencil 

 is to all intents and purposes finished, but has to undergo a variety of 

 processes, which change this crude pencil from a rough, square stick, 

 covered with glue, into a smooth, polished, rounded or curved, 

 stamped, gilt, headed, and, in fact, a completed -article, ..which every 

 man, woman or child handles with pleasure and satisfaction, without 

 pausing to consider that a lead pencil has passed through twenty-five 

 hands before it is complete. The, ever pointed pencils are aiiade. iii 



