Proceedings of the Polytechnic Association. 873 



ite is not used up for the manufacture of ci'ucibles alone ; a very large 

 amount is wanted for the lustre, so-called British or jVTexican lustre, 

 which froms a very considerable branch of industry ; there are no 

 less than lifty manufacturers of lustre in the United States, of which 

 Dixon & Co. put up 150 gross, or 20,000 packages of the lustre per 

 day. Large establishments exist in Philadelphia, Boston, Cleveland, 

 and in this city, so that we may compute the amount manufactured 

 in the United States at 1,000 gross per day. 



In conclusion, a few remarks on the great American locality of 

 graphite, situated at Ticonderoga, may give an idea of the extent to 

 wliich this branch of industry is now carried on. The mining prop- 

 erty of the American Graphite Company is comprised in the Arthur 

 and Joes mountains, at Ticonderoga, on Lake Champlain, and at 

 Warrensburgh, on Lake G-eorge ; the latter contains veins of the 

 granular or compact graphite, which, after having been purified, 

 furnishes excellent pencil lead, while the Ticonderoga mines have 

 only the foliated graphite, containing disseminated carbonate of lime, 

 wliich requires to be concentrated by proper machinery. This is 

 done in the most practical manner, so that from five to ten tons per 

 day are forwarded ready for crucible makers. 



Not less than 150 veins or deposits have already been discovered ; 

 some of them have been worked to the depth of several hundred 

 feet ; parallel veins are constantly discovered at a distance of twelve 

 feet. 



The company prepares the graphite for all the uses known, from 

 stove polish, to the finest lubricator for journals of engines, pencil 

 and crucible lead. 



The following pa]3er was then presented : 



Tempering Steel. 



Mr. Norman TViard. — If we take a plate of highly carbonized cast- 

 steel one-hundredth of an inch in thickness (the thinner the better), 

 heat it between two cast-iron plates (which will prevent it from 

 being decarbonized), and let it slip, when hot, from between them, 

 edgewise into cold water, it will be made hard enough to cut glass. 

 A plate of steel, one inch thick, so treated, although no heavier than 

 before, will be slightly larger ; if it were smaller its hardness might 

 be attributed to condensation. If its surface be rubbed briglit and it 

 is slightly and slowly heated, it M-ill soon assume a straw color, which 

 indicates a certain degree of reduced hardness known to the expert. 



