A paper read by request at the Albany Institute, was the germ of the following pages; its publication in this form, I considered would furnish engineers, contractors and railroad directors, who occasionally apply to me for particulars as to the use of Nitro-Glycerin in the Hoosac Tunnel, with detailed information impossible to condense in a business letter. Hurriedly composed during the spare hours of a manufacture involving grave responsibility, the writer weighted with the additional task of defeating an attempt to monopolize the use (not the manufacture) of Nitro-Glycerin throughout the United States, whilst the subject itself, “Explosives, and firing mines by Electricity,” constantly demanded experimental research, this work has not the arrangement nor the completeness I could desire; but the author hopes it will create a more favorable regard in the public mind, towards the most powerful blasting agent known, by correcting errors in respect to its properties, and the casualties attending its use; and assist miners and contractors to a more intelligent acquaintance with some of the materials the present advanced state of engineering progress has brought into practical use. GEO. M. MOWBRAY. North Adams, Mass., June 1st, 1872. CONTENTS. CHAPTER I. Nitro-Glycerin—Introduction of the explosive in New York, San Francisco, Lake Superior, and the Hoosac Tunnel, Massachusetts; Accidents; Reports of Engineers Thos. A. Doane, W. P. Granger and B. D. Frost, of the Manufacturer; Miners’ statement. CHAPTER II. Submarine Blasting—Erie Harbor—Dimon’s Reef, New York—Coenties Reef, N. Y.—Oil Wells, Penn. CHAPTER III. Nitro-Glycerin considered in its chemical details. CHAPTER IV. Electricity in blasting operations. CHAPTER V. The Tri-Nitro-Glycerin manufactured at the Hoosac Tunnel—How Tri-Nitro-Glycerin is made—How stored—How Gutta-Percha is purified—How the Exploders are manufactured. CHAPTER VI. Explosive mixtures. CHAPTER VII. Nitro-Glycerin patents and litigation. CHAPTER VIII. Hoosac Tunnel—Drilling by machine—Blasting with Powder—Nitro-Glycerin. DIRECTIONS FOR HANDLING AND USING TRI-NITRO-GLYCERIN. APPENDIX. A. Memoranda for Contractors. B. Over-sensitive Exploders. C. Professor Abel on effects of initial explosion on explosives. D. Car freighted with 4,800 lbs. Nitro-Glycerin off the track. E. Accidents at the Hoosac Tunnel. ILLUSTRATIONS.