From other of its alloys, knives, axes, swords, and all cutting implements may receive and hold an edge not surpassed by the best tempered steel.  Hulot, director in the postage stamp department, Paris, asserts that 120,000 blows will exhaust the usefulness of the cushion of the stamp machine, and this number of blows is given in a day; and that when a cushion of aluminum bronze was substituted, it was unaffected after months of use.

If we have found a metal that possesses both tensile strength and resistance to compression; malleability and ductility—­the quality of hardening, softening, and toughening by tempering; adaptability to casting, rolling, or forging; susceptibility to luster and finish; of complete homogeneous character and unusually resistant to destructive agents—­mankind will certainly leave the present accomplishments as belonging to an effete past, and, as it were, start anew in a career of greater prospects.

This important material is to be found largely in nearly all the rocks, or as Prof.  Dana has said, “Nearly all rocks are ore-beds of the metal.”  It is in every clay bank.  It is particularly abundant in the coal measures and is incidental to the shales or slates and clays that underlie the coal.  This under clay of the coal stratum was in all probability the soil out of which grew the vegetation of the coal deposits.  It is a compound of aluminum and other matter, and, when mixed with carbon and transformed by the processes of geologic action, it becomes the shale rock which we know and which we discard as worthless slate.  And it is barely possible that we have been and are still carting to the refuse pile an article more valuable than the so greatly lauded coal waste or the merchantable coal itself.  We have seen that the best alumina ore contains only fifty-four per cent. of metal.

The following prepared table has been furnished by the courtesy and kindness of Mr. Alex.  H. Sherred, of Scranton.

ALUMINA.

Blue-black shale, Pine Brook drift 27.36 Slate from Briggs’ Shaft coal 15.93 Black fire clay, 4 ft. thick, Nos. 4 and 5 Rolling Mill mines 23.53 First cut on railroad, black clay above Rolling Mill 32.60 G vein black clay, Hyde Park mines 28.67

It will be seen that the black clay, shale, or slate, has a constituent of aluminum of from 15.93 per cent., the lowest, to 32.60 per cent., the highest.  Under every stratum of coal, and frequently mixed with it, are these under deposits that are rich in the metal.  When exposed to the atmosphere, these shales yield a small deposit of alum.  In the manufacture of alum near Glasgow the shale and slate clay from the old coal pits constitute the material used, and in France alum is manufactured directly from the clay.