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tation have brought the fruits of the tropics in great abundance to the doors of the dwellers of the north, and from the shores of the Pacific to the Atlantic and across the Atlantic to Europe. A train of refrigerator cars in California laden with delicious assorted fruits, and provided with fan blowers driven by the car axles to force the air through ice chambers, from whence it is distributed by perforated pipes through the fruit chambers, and wherein the temperature is maintained at about 40° Fah., can be landed in New York four days after starting on its journey of 3,000 miles, with the fruits in perfect condition.

But the public is still excited and wondering over the new king of refrigeration-liquid air.

As has been stated, the compression of air to produce cold is a modern discovery applied to practical uses, and prominent among the inventors and discoverers in this line have been Prof. Dewar and Charles E. Tripler.

Air may be compressed and heat generated in the process withdrawn until the temperature of the air is reduced to 312° below zero, at which point the air is visible and to a certain extent assumes a peculiar material form, in which form it can be confined in suitable vessels and used as a refrigerant and as a motor of great power when permitted to re-expand. It is said that it was not so long ago when Prof. Dewar produced the first ounce of liquid air at a cost of $3,000, but that now Mr. Tripler claims that he can produce it by his apparatus for five cents a gallon.

Refrigeration is at present its most natural and obvious use, and it is claimed that eleven gallons of the material when gradually expanded has the refrig

erating power of one ton of ice. Its use of course for all purposes for which cold can be used is thus assured. It is also to be used as a motor in the running of various kinds of engines. It is to be used as a great alleviator of human suffering in lowering and regulating the temperature of hospitals in hot weather, and in surgical operations as a substitute for anæsthetics and cauterising agents.

It was one of the marvellous attractions at the great Paris Exposition of 1900.

Lighting is closely allied to the various subjects herein considered, but consideration of the various modes and kinds of lamps for lighting will be reserved for the Chapter on Furniture for Houses, etc.

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CHAPTER XIV.

METALLURGY.

"NIGH on the plain, in many cells prepared,
That underneath had veins of liquid fire
Sluiced from the lake, a second multitude
With wondrous art founded the massy ore;
Severing each kind, and scumm'd the bullion dross;
A third as soon had formed within the ground

A various mould, and from the boiling cells

By strange conveyance fill'd each hollow nook;
As in an organ, from one blast of wind,

To many a row of pipes the sound board breathes."
-Paradise Lost.

EVER since those perished races of men who left no other record but that engraven in rude emblems on the rocks, or no other signs of their existence but in the broken tools found buried deep among the solid leaves of the crusted earth, ever since Tubal Cain became "an instructor of every artificer in brass and iron," the art of smelting has been known. The stone age flourished with implements furnished ready-made by nature, or needing little shaping for their use, but the ages of metal which followed required the aid of fire directed by the hand of man to provide the tool of iron or bronze.

The Greeks claimed that the discovery of iron was theirs, and was made at the burning of a forest on the mountains of Ida in Crete, about 1500 B. C., when the ore contained in the rocks or soil on which the forest stood was melted, cleansed of its impurities, and then collected and hammered. Archeolo

gists have deprived the Greeks of this gift, and carried back its origin to remoter ages and localities.

Man first discovered by observation or accident that certain stones were melted or softened by fire, and that the product could be hammered and shaped. They learned by experience that the melting could be done more effectually when the fuel and the ore were mixed and enclosed by a wall of stone; that the fire and heat could be alone started and maintained by blowing air into the fuel-and they constructed a rude bellows for this purpose. Finding that the melted metal sank through the mass of consumed fuel, they constructed a stone hearth on which to receive it. Thus were the first crude furnace and

hearth invented.

As to gold, silver and lead, they doubtless were found first in their native state and mixed with other ores and were hammered into the desired shapes with the hardest stone implements.

That copper and tin combined would make bronze was a more complex proceeding and probably followed instead of preceding, as has sometimes been alleged, the making of iron tools. That bronze relics were found apparently of anterior manufacture to any made of iron, was doubtless due to the destruction of the iron by that great consumer-oxygen.

What was very anciently called "brass" was no doubt gold-coloured copper; for what is modernly known as brass was not made until after the discovery of zinc in the 16th century and its combination with copper.

Among the "lost arts" re-discovered in later ages are those which supplied the earliest cities with ornamented vessels of gold and copper, swords of steel that bent and sprung like whalebones, castings that

had known no tool to shape their contour and embellishments, and monuments and tablets of steel and brass which excite the wonder and admiration of the best "artificers in brass and iron" of the present day.

To understand and appreciate the advancements that have been made in metallurgy in the nineteenth century, it is necessary to know, in outline at least, what before had been developed.

The earliest form of a smelting furnace of historic days, such as used by the ancient Egyptians, Hebrews, and probably by the Hindoos and other ancient peoples, and still used in Asia, is thus described by Dr Ure:

"The furnace or bloomary in which the ore is smelted is from 4 to 5 feet high; it is somewhat pearshaped, being about 5 feet wide at bottom and 1 at top. It is built entirely of clay. There is an opening in front about a foot or more in height which is filled with clay at the commencement, and broken down at the end of each smelting operation. The bellows are usually made of two goatskins with bamboo nozzles, which are inserted into tubes of clay that pass into the furnace. The furnace is filled with charcoal, and a lighted coal being introduced before the nozzle, the mass in the interior is soon kindled. As soon as this is accomplished, a small portion of the ore previously moistened with water to prevent it from running through the charcoal, but without any flux whatever, is laid on top of the coals, and covered with charcoal to fill up the furnace. In this manner ore and fuel are supplied and the bellows urged for three or four hours. When the process is stopped and the temporary wall in front broken down the bloom is removed with a pair of tongs from the bottom of the furnace."

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