nace. A graphite of uniform and superior quality is obtained. It contains about 90 per cent. of carbon, and the remaining 10 per cent. consists of matter as inert as the graphite itself.

Lamp-black—that is, soot or the black of smoke—represents almost pure carbon when prepared with proper care. The raw materials for its manufacture are numerous, including rosin, naphtha, coal-tar products, tallow, or any oily substance which will burn with a smoky flame, provided its use is not prohibited by considerations of cost.

These materials are burned according to their nature either in burners or heated kettles in such a manner as to produce a very smoky flame. This smoke is then collected in bags or chambers.

Lamp-blacks are not changed by air or