The Nitro-Glycerin is by this time thoroughly washed and ready to store in the magazine, 300 feet distant, to which it is carried in a couple of copper pails at a time, by a man with a yoke, similar to what milkmen use for carrying their pails. Curious thought, that a man carrying a couple of harmless looking pails with only a little colorless fluid in them, should have enough explosive matter about him to annihilate a regiment.
In the magazine the Nitro-Glycerin is poured into “crocks,” as they are called, earthenware jars holding 60 lbs. These crocks are then placed in a wooden tank 2½ feet deep, which holds 20 of them, and immersed to within six inches from the top of the jars in water warmed by a small pipe from the boiler, to raise the temperature to 70°, at which temperature it is kept all the time, as nearly as possible. They remain in this water for about 72 hours, during which time any impurities still remaining rise to the surface as scum, and are skimmed off with a spoon. The Nitro-Glycerin is then chemically pure, transparent as water, refracts light powerfully, and is ready for packing. The tin cans, lined with paraffine and containing 56 lbs. each, are placed in a shallow wooden trough, and the Nitro-Glycerin being poured from the crocks into copper cans, is again poured into the tins through a gutta-percha funnel, the bottom of the trough being covered with a thick layer of plaster of paris, which absorbs and renders harmless any drops of Nitro-Glycerin that may be spilt. The tins when filled are then placed in a wooden trough containing iced water, or ice and salt, where the Nitro-Glycerin is slowly crystallized or congealed; in this condition, it is stored away in small magazines 300 feet distant, in amounts of 30 to 40 cans each, until required for use.
When the Nitro-Glycerin is to be conveyed over the mountains, the tins are packed in open wooden boxes, with two inches of sponge at the bottom, and four rubber tubes underneath; these are long enough to allow the ends to come one inch over the top of the tin on opposite sides, thus interposing two elastic tubes between the outside of the tin and the inside of the wooden box, rendering it perfectly safe to carry. Each tin is cellular, i. e., from the top of each tin to the bottom a tube passes, about ten inches deep and 1½ inch in diameter, for the purpose of thawing the congealed Nitro-Glycerin when the blaster is ready to use it, liquefaction being effected with water of 70° to 90°. The tins being closed with a cork wrapped in bladder, are put into a sleigh or wagon, covered in summer with a layer of ice and blankets, and may thus be carried any distance in this purified crystalline state, as safely as so many tubs of butter.
The reflecting reader will note the care taken to purify the Nitro-Glycerin; it occupies 1½ hours to make it, about 72 hours to purify, and about 48 hours to congeal or crystallize it. And yet there are parties who attempt to make and vend Nitro-Glycerin, and induce miners and contractors to use it, taken direct from the precipitating tank, with all its impurities tending to decomposition, and requiring only time and moderate temperature for spontaneous explosion; hence, I believe many accidents.
Proceeding back to the factory, two ice-houses will be noticed, capable of containing 400 tons of ice, required for crystallizing Nitro-Glycerin in summer. There is a small engine-house with a boiler of fifteen horse power, and engine of about ten horse power; this latter, to pump water into the washing tank, run the two “blowers,” and give power in the gutta-percha factory. The air is not pumped directly into the pipe which distributes it to the pitchers, as the pressure would not be always uniform; but into two receivers under the floor of the factory, whence it is evenly distributed, and deprived of watery vapor, which if blown into the pitchers would raise the temperature and vitiate the product.
Attached to the factory is a building about 90 feet long, for covering the copper wire (used in exploding) with gutta-percha, so as to render the insulation perfect. The first process is to purify the crude gutta-percha which is imported in blocks about a foot long. This is placed against a rasping machine with toothed knives about four inches apart, which crush and tear the gutta-percha to pieces, delivering it into a trough of water. The impurities sink, while the gutta-percha floats. It is then warmed in a steam jacketed kettle, and when still plastic is put into another tearing or rasping machine with another series of knives set closer together, from this it drops into a trough of clean water, more dirt separating. This is repeated two or three times, as it is most important that no extraneous matter should be retained in the gutta-percha, because it would interfere with perfect insulation, and so place in jeopardy the lives of several men. It is again steamed and put into a “masticator” consisting of a fluted roller working in a steam jacket; here it is “chawed up” for about six hours, until it arrives at a proper consistence; it is then passed between two smooth cylinders heated by steam, and transferred thence into a cylinder, where it is pressed through gauze wire, under a pressure of four tons to the inch. Being thoroughly cleansed, it is then steamed, masticated and pressed between the cylinders, and is ready to cover the copper wire. Five wires at a time, horizontally parallel to one another, are passed through a gun metal mould with a disc at the further end perforated with five holes but little larger than the wires themselves, placed at the base of an upright cylinder. The gutta-percha is inserted in the top of this cylinder, and a pressure of 95 tons is put upon it by means of a screw, when it is pressed into slots in the mould surrounding the wires, which are then drawn from the holes in the disc, through a trough of water 80 feet long, and back again: it is then wound on drums ready for use. The “leading” wire receives two coatings, separate discs having larger bores being attached to the brass cylinder.
A house is attached to the factory, for the foreman and his family.
Perfect system pervades this factory, and is absolutely necessary in the manufacture of Nitro-Glycerin, to ensure safety. The steadiest men possible are selected for the work, and the foreman of the gutta-percha department, Mr. Robert Wallace, who has charge of the machinery, is a skilful machinist and a thoroughly trustworthy Scotchman. He has four sons employed, of whom one takes charge of the works at Maysville, Kentucky, another, is foreman of the Nitro-Glycerin factory.
Three men are employed in the acid house, working in three shifts of eight hours each, but they do not actually work more than seven hours; every movement is like clock work, every man has his place and special duty, which he is expected to perform at the proper time. In the morning, at 7 or 7½ a. m., two men dump the carboys of acid into the soapstone tank and mix them, while a third is filling the glass jars with glycerin. This operation takes about an hour. One draws the acid, another weighs it, and a third carries it to the troughs. After an interval during which the acids cool, three men attend closely to the converting of glycerin into Tri-Nitro-Glycerin, knowing that their safety, and the safety of every man on the works, depends on themselves alone, during this process. After the Nitro-Glycerin is dumped into the water tank, two men are employed in washing it, down stairs, while two wash the stone pitchers with water; more water, temperature about 60°, is swilled on the floors so as to keep them scrupulously clean and perfectly free from atoms of Nitro-Glycerin, which, stepped upon while the men are at work, might send them to eternity, and the building to smithereens. The room is then prepared for next day’s operations, and by about one or two o’clock, after six, or at most seven hours’ work, the day’s task is done. Mr. Wilson, in charge of the purifying process, canning, and preparing for shipment, has now been over four years at this work.