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Air may be compressed and heat generated in the process withdrawn until the temperature of the air is reduced to 312° below zero, at which point the air is visible and to a certain extent assumes a peculiar material form, in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 is now 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.

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