Note 3 — Chapter II
Reading edition
Analyses recently made by Mr. C. Hoffman, of the Geological Survey of Canada, show that beds of graphitic gneiss, some of them 8 feet in thickness, contain as much as 25·5 to 30 per cent. of carbon, the remaining earthy matter consisting principally of silica, alumina, and lime. The graphite from veins was nearly pure carbon, containing from 97·6 to 99·8 per cent. of that substance.