passed through them than by combustion, and the process is much used in making clock and watch springs.

One way of hardening plates, especially armour plates, by what is called the Harveyized process, is by embedding the face of the plate in carbon, protecting the back and sides with sand, heating to about the melting point of cast iron, and then hardening the face by chilling, or otherwise.

Coating with Metal.-Although covering metal with metal has been practised from the earliest times, accomplished by heating and hammering, it was not until this century that electro-plating, and plating by chemical processes, as by dipping the metal into certain chemical solutions, and by the use of automatic machinery, were adopted. It was in the early part of the century that Volta discovered that in the voltaic battery certain metallic salts were reduced to their elements and deposited at the negative pole; and that Wollaston demonstrated how a silver plate in bath of sulphate of copper through which a current was passed became covered with copper. Then in 1838, Spencer applied these principles in making casts, and Jacobi in Russia shortly after electro-gilded a dome of a cathedral in St. Petersburg. Space will not permit the enumeration of the vast variety of processes and machines for coating and gilding that have since followed.

Metal Founding.-The treatment of metal after it flows from the furnaces, or is poured from the crucibles into moulds, by the operations of facing, drying, covering, casting and stripping, has given rise to a multitude of machines and methods for casting a great variety of objects. The most interesting inventions in this class have for their object

the chilling, or chill hardening, of the outer surfaces of articles which are subject to the most and hardest wear, as axle boxes, hammers, anvils, etc., which is effected by exposing the red-hot metal to a blast of cold air, or by introducing a piece of iron into a mould containing the molten metal.

In casting steel ingots, in order to produce a uniform compact structure, Giers of England invented soaking pits of sand" into which the ingot from the mould is placed and then covered, so that the heat radiating outward re-heats the exterior, and the ingot is then rolled without re-heating.

Sheet Metal Ware.-Important improvements have been made in this line. Wonderful machines have been made which, receiving within them a piece of flat metal, will, by a single blow of a plunger in a die, stamp out a metal can or box with tightly closed seams, and all ready for the cover, which is made in another similar machine; or by which an endless chain of cans are carried into a machine and there automatically soldered at their seams; and another which solders the heads on filled cans as fast as they can be fed into the machine.

Metal Personal Ware.-Buckles, clasps, hooks and eyelets, shanked buttons, and similar objects are now stamped up and out, without more manual labour than is necessary to supply the machines with the metal, and to take care of the completed articles.

Wire Working.-Not only unsightly but useful barbed wire fences, and the most ornamental wire work and netting for many purposes, such as fences, screens, cages, etc., are now made by ingenious machines, and not by hand tools.

In stepping into some one of the great modern works where varied industries are carried on under

one general management, one cannot help realising the vast difference between old systems and the new. In one portion of the establishment the crude ores are received and smelted and treated, with a small force and with ease, until the polished metal is complete and ready for manipulation in the manufacture of a hundred different objects. In another part ponderous or smaller lathes and planing machines are turning forth many varied forms; in quiet corners the boring, drilling, and riveting machines are doing their work without the clang of hammers; in another, an apparently young student is conducting the scientific operation of coating or gilding metals; in another, girls may be seen with light machines, stamping, or burnishing, or assembling the different parts of finished metal ware; and the motive power of all this is the silent but allpowerful electric current received from the smoothrunning dynamo giant who works with vast but unseen energy in a den by himself, not a smoky or a dingy den, but light, clean, polished, and beautiful as the workshop of a god.

CHAPTER XVI.

ORDNANCE, ARMS AND EXPLOSIVES.

ALTHOUGH the progress in the invention of firearms of all descriptions seems slow during the ages preceding this century, yet it will be found on investigation that no art progressed faster. No other art was spurred to activity by such strong incentives, and none received the same encouragement and reward for its development. The art of war was the trade of kings and princes, and princely was the reward to the subject who was the first to invent the most destructive weapon. Under such high patronage most of the ideas and principles of ordnance now prevailing were discovered or suggested, but were embodied for the most part in rude and inefficient contrivances.

The art waited for its success on the development of other arts, and on the mental expansion and freedom giving rise to scientific investigation and results.

The cannon and musket themselves became the greatest instruments for the advancement of the new civilisation, however much it was intended otherwise by their kingly proprietors, and the new civilisation returned the compliment through its trained intellects by giving to war its present destructive efficiency.

To this efficiency, great as the paradox may seem, Peace holds what quiet fields it has, or will have, until most men learn to love peace and hate the arts of war.

As to the Chinese is given the credit for the invention of gunpowder, so they must also be regarded as the first to throw projectiles by its means. But their inventions in these directions may be classed as fireworks, and have no material bearing on the modern art of Ordnance. It is supposed that the word cannon," is derived from the same root as cane," originally signifying a hollow reed; and that these hollow reeds or similar tubes closed at one end were used to fire rockets by powder.

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It is also stated that the practice existed among the Chinese as early as 969 A.D. of tying rockets to their arrows to propel them to greater distances, as well as for incendiary purposes.

This basic idea had percolated from China through India to the Moors and Arabs, and in the course of a few centuries had developed into a crude artillery used by the Moors in the siege of Cordova in 1280. The Spaniards, thus learning the use of the cannon, turned the lesson upon their instructors, when under Ferdinand IV. they took Gibraltar from the Moors in 1309. Then the knowledge of artillery soon spread throughout Europe. The French used it at the siege of Puy Guillaume in 1338, and the English had three small guns at Crecy in 1346. These antique guns were made by welding longitudinal bars of iron together and binding them by iron rings shrunk on while hot. Being shaped internally and externally like an apothecary's mortar, they were called mortars or bombards. Some were breech-loaders, having a having a removable chamber at the breech into which the charge of powder was inserted behind the ball. The balls were stone. These early cannon, bombards, and mortars were mounted on heavy solid wooden frames and moved