Berthollet, Graham, and a host of others in England, France, and Germany, advanced the art. The highest skilled mechanics, like Clegg of England, supplied the apparatus. He it was who invented a gas purifier, liquid gas meter, and other useful contrivances.

As the character of the gas as an illuminator de pends on the quantity of hydro-carbon, or olefiant elements it contains, great efforts were made to invent processes and means of carbureting it.

The manufacture of gas was revolutionised by the invention of water gas. The main principle of this process is the mixture of hydrogen with the vapour of some hydro-carbon: Hydrogen burns with very little light and the purpose of the hydro-carbon is to increase the brilliancy of the flame. The hydrogen gas is so obtained by the decomposition of water, effected by passing steam through highly heated coals.

Patents began to be taken out in this line in England in 1823-24; by Donovan in 1830; Geo. Lowe in 1832, and White in 1847. But in England water gas could not compete with coal gas in cheapness. On the contrary, in America, especially after the petroleum wells were opened up, and nature supplied the hydro-carbon in roaring wells and fountains, water gas came to the front.

The leading invention there in this line was that of T. S. C. Lowe of Morristown, Pennsylvania, in 1873. In Lowe's process anthracite coal might be used, which was raised in a suitable retort to a great heat, then superheated steam admitted over this hot bed and decomposed into hydrogen and carbonic oxide; then a small stream of naphtha or crude petroleum was thrown upon the surface of the burning coal, and from these decompositions and mixtures a rich

olefiant product and other light-giving gases were produced.

The Franklin Institute of Philadelphia in 1886 awarded Lowe, or his representatives, a grand medal of honour, his being the invention exhibited that year which in their opinion contributed most to the welfare of mankind.

A number of inventors have followed in the direction set by Lowe. The largest part of gas manufacture, which has become so extensive, embodies the basic idea of the Lowe process.

The competition set up by the electricians, espe cially in the production of the beautiful incandescent light for indoor illumination, has spurred inventors of gas processes to renewed efforts much to the benefit of that great multitude who sit in darkness until corporations furnish them with light.

It was found by Siemens, the great German inventor of modern gas regenerative furnace systems, that the quality of the gas was much improved, and a greater intensity of light obtained, by heating the gases and air before combustion-a plan particularly adapted in lighting large spaces.

To describe in detail the large number of inventions relating to the manufacture of gas would require a huge volume the generators, carburetors, retorts, mixers, purifiers, metres, scrubbers, holders, condensers, governors, indicators, registers, chargers, pressure regulators, etc., etc.

It was a great convenience outside of towns and cities, where gas mains could not be laid, to have domestic plants and portable gas apparatus, worked on the same principles, but in miniature form, adapted to a single house, but the exercise of great ingenuity was required to render such adaptation successful.

In the use of liquid illuminants, which need a wick to feed them, the Argand burner—that arrangement of concentric tubes between which the wick is confined-although invented by Argand in 1784, yet has occupied a vast field of usefulness in connection with the lamps of the nineteenth century.

A dangerous but very extensively used illuminating liquid before coal oil was discovered was camphene, distilled from turpentine. It gave a good light but was not a safe domestic companion.

Great attention has recently been paid to the production of acetylene gas, produced by the reaction between calcium carbide and water. The making of the calcium carbide by the decomposition of mixed pulverised lime and coal by the use of a powerful electric battery, is a preliminary step in the production of this gas, and was a subsequent discovery.

The electric light, acetylene, magnesium, and other modern sources of light, although they may be more brilliant and intense than coal gas, cannot compete in cheapness of production with the latter. Thus far illuminating coal gas is still the queen of artificial lights.

After gas was fairly started in lighting streets and buildings its adaptation to lamps followed; and among the most noted of gas lamps is that of Von Welsbach, who combined a bunsen gas flame and a glass chimney with a "mantle" located therein. This mantle is a gauze-like structure made of refractory quartz, or of certain oxides, which when heated by the gas flame produce an incandescent glow of intense brilliancy, with a reduced consumption of gas.

CHAPTER XXXI.

BRICK, POTTERY, GLASS, PLASTICS.

WHEN the nineteenth century dawned, men were making brick in the same way for the most part that they were fifty centuries before. It is recorded in the eleventh chapter of Genesis that when "the whole earth was of one language and one speech, it came to pass as they journeyed from the east that they found a plain in the land of Shinar; and they dwelt there, and they said to one another, Go to, let us make brick and burn them thoroughly, And they had brick for stone, and slime had they for mortar." Then commenced the building of Babel. Who taught the trade to the brick-makers of Shinar?

The journey from the east continued, and with it went brick making to Greece and Rome, across the continent of Europe, across the English channel, until the brick work of Cæsar, stamped by the trade mark of his legions, was found on the banks of the Thames, and through the fields of Caerleon and York.

Alfred the Great encouraged the trade, and the manufacture flourished finely under Henry VIII., Elizabeth and Charles I.

As to Pottery:-Could we only know who among the peoples of the earth first discovered, used, or invented fire, we might know who were the first makers of baked earthenware. Doubtless the art of pottery arose before men learned to bake the plastic clay, in

that groping time when men, kneading the soft clay with their fingers, or imprinting their footsteps in the yielding surface and learning that the sun's heat stiffened and dried those forms into durability, applied the discovery to the making of crude vessels, as children unto this day make dishes from the tenacious mud. But the artificial burning of the vessels was no doubt a later imitation of Nature.

Alongside the rudest and earliest chipped stone implements have been found the hollow clay dish for holding fire, or food, or water. "As the fragment of a speech or song, a waking or a sleeping vision, the dream of a vanished hand, a draught of water from a familiar spring, the almost perished fragrance of a pressed flower call back the singer, the loved and lost, the loved and won, the home of childhood, or the parting hour, so in the same manner there linger in this crowning decade of the crowning century bits of ancient ingenuity which recall to a whole people the fragrance and beauty of its past." Prof. O. T. Mason. The same gifted writer, adds: "Who has not read, with almost breaking heart, the story of Palissy, the Huguenot potter? But what have our witnesses to say of that long line of humble creatures that conjured out of prophetic clay, without wheels or furnace, forms and decorations of imperishable beauty, which are now being copied in glorified material in the best factories of the world? In ceramic as well as textile art the first inventors were women. They quarried the clay, manipulated it, constructed and decorated the ware, burned it in a rude furnace and wore it out in a hundred uses.'

From the early dawn of human history to its present noonday civilisation the progress of man may be traced in his pottery. Before printing was an art, he