2. The best Nitro-Glycerin may be simply fired, or only exploded, or its full blasting effects achieved, precisely according to the initial velocity or force used to start the explosion; two cents in an exploder therefore may save ten dollars in a blast.
3. Ten per cent. of water diffused through Nitro-Glycerin, giving it a milky appearance (Nitro-Glycerin emulsion), will diminish its effective blasting results 30 per cent.
4. Thirty per cent. more blasting power is evolved, when the Nitro-Glycerin reaches the bare rock of the drill hole, than when, by insertion in cartridge, the metal of the cartridge and a layer of air or water are interposed between the blasting gases and the rock.
5. Pure Nitro-Glycerin may be safely stored, and does not readily change; impure Nitro-Glycerin needs only time and temperature to explode spontaneously.
6. In hard pan, or indurated clay, Nitro-Glycerin is not so economical as powder; in granite, gneiss, hornblende, quartz and other hard rocks, the harder the better, especially in large erratic boulders, the larger the better, Nitro-Glycerin will enable the tunneling, cut or block-holing, to be performed at half the cost as compared with gunpowder.
The term, “over-sensitive,” has been used in the foregoing pages, and applied to exploders. Mr. Joseph Dowse, of Lockport, Illinois, applied “fulminate of copper” (a discovery of Dr. John Davy) as a priming for exploders, and patented the application, observing in his patent that parties unaccustomed to the preparation of fulminates had better leave this preparation alone. The sequel shows Mr. Dowse’s caution was not superfluous. Two manufacturers, provoked by the commercial inconvenience of the constant return of exploders owing to their inefficiency, have resorted to this “over-sensitive” priming, and received the following warnings:
In 1869, Mr. Stowell was standing in the office, on Sudbury street, Boston, whilst Mr. H. Julius Smith was packing 200 exploders in a rubber bag, in which an ebonite electric machine had been placed. Mr. Stowell remarked, “Is it safe to crowd them into a bag like that?” “Oh yes, perfectly safe,” was the reply, when instantly 170 out of the 200 exploded, severely burning and injuring both Smith and Stowell, the latter being confined to his bed for five weeks in consequence.