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being adopted deliberately. By the sixteenth century the demands of the iron industry were thinning the forests to such an extent that an Act of Queen Elizabeth prohibited the cutting of timber for that purpose in some districts, and a later one of the same reign forbade the construction of new ironworks in Kent, Surrey, and Sussex. In 1611 Simon Sturtevant patented a method for using mineral coal in place of charcoal, and he was followed in 1619 by Dud Dudley, who advocated the same change ; but the innovation met with so much opposition from the ironmasters that it failed to establish itself. Coal was reintroduced in the iron industry in 1713 at Coalbrookdale, but the methods it entailed were not thoroughly understood, and production decreased until, about the middle of the eighteenth century, the manufacture of cast iron with coke in the high furnace was invented. The substitution of coke. for charcoal, and the invention of machinery, such as Watt's steam-engine, which required coal as fuel, were partly the cause of that migration of industry to the towns of the great coalfields which marked the beginning of the Industrial Revolution. Nowadays the furnace scooped by prehistoric iron-workers in the ground or in a bank has been succeeded by the modern blast furnace, a hollow tower from 40 to 100 feet in height, and with a capacity of from 500 to 25,000 cubic feet.

It is possible that the use to any considerable extent of coal, on which the modern development of the iron industry depended, first began in Britain. It was at any rate in household use in Anglo-Saxon times, as early as the ninth century A.D. About the end of the thirteenth century it began to be employed in manufacture in London, but its use was unpopular, as it was supposed to be injurious to health. In 1306 its use was

actually prohibited, but in spite of this it was soon the general fuel in London owing to the high price of wood. With the invention of the steam-engine it became the main source of power.

It was believed at one time that our coal supplies were inexhaustible. This is by no means the case, and it is a question of the present day to what extent it is prudent to convert them into electric power rather than to consume them wastefully as fuel. The replacement to a great extent of steam power by electricity is likely in the near future to bring about great changes in our daily life. At present electric power is dependent on magnetic iron, and, in this country, on the energy stored in coal ; but it may not be long before the coal era is brought to an end, because science has grasped the means of utilizing directly the energy of sun, wind, and tide, and of releasing the energy of the atom.

CHAPTER XVII

MAN DISCOVERS THE UNIVERSE

S:

a

OME time between 1000 and 500 B.C. all over
Europe the substitution of iron for bronze as

the metal of everyday use had ushered in the last division of prehistoric time. When the characters of the different alphabets were devised written language began, and man passed from the darkness of immense prehistoric ages, upon which only a little light is shed by relics found in rocks, caves, and tombs, into the dawn of history. Written history in Europe goes back, then, between two and three thousand years ; it is believed that man has existed in Europe at least a hundred and fifty thousand years. What master-minds led him in his progress from a mere struggle for existence with teeth and hands, sticks and stones, a struggle during which he had to pit his cunning against the strength and fleetness of wild beasts, and to compete with them for the possession of a wild beast's lair, to the use of fire, the building of houses, and the fashioning of implements of stone and metal, we shall never know. These unknown thinkers were the eyes of a humanity groping in darkness. Through their vision existence, when history opens, had lost half its material terrors. Life was no longer for all men a struggle that began afresh every day. It had become possible for some to give themselves to a life of thought. Curiosity was born as the human spirit awoke. There was plenty for it to work on. Man had to discover the universe ;

he had to discover the earth; he had to discover

l himself.

The beginnings of trade would make north and south, east and west, acquainted with one another through strange tales of different customs, climates, beasts, and men,

The Anthropophagi, and men whose heads
Do

grow beneath their shoulders. Primitive religion and primitive art would spring from man's curiosity about himself, his desire to know why he is here and where he is going, and to transmit to others his impressions of life.

Perhaps as early as the mind of man was capable of thought at all the mere succession of days and nights must have set him wondering about the sun and moon and stars, and devising explanations to satisfy his own and others' questioning.

Earliest history shows us communities of men already possessed of elaborate religious systems and beautiful forms of art, with extensive trade relations, and with theories of the universe which were something more than “ a wild surmise.” It is one of the greatest wonders in the record of the human race that even while men had but a scanty knowledge of the earth on which they were placed there were some whose minds were already set upon obtaining an answer to the riddles of the universe.

Probably the earliest star-gazers were Egyptian priests, evidence of whose astronomical knowledge exists in the construction of the pyramids, which were built several thousand years B.C. Indian and Chinese records refer to observations made between two and three thousand years B.C.; and not much later Chaldean priests in Babylon were not only acquiring real astronomical knowledge, but laying the foundations of that false science called astrology which, professing to predict wars, pestilences, and famines by observation of the heavens, to interpret a man's fate by the position of the stars at his birth, and to choose a favourable date for the beginning of an enterprise, has held such a fascination for the human mind that belief in it, as witnessed for instance by Old Moore's Almanack, is not quite extinct even at the present day. Based as it was upon credulity and superstition, astrology, like other false sciences, stimulated a desire for true knowledge, and so was not without its uses.

While wishing to give all due credit to these ancient astronomers, we know little really about the extent of their knowledge, except that they seem to have devoted themselves to making observations rather than to seeking for causes. The first really historical astronomers were the Greeks, who may have derived their astronomical skill from the Chaldeans, the Egyptians, or from men of their own race. But before history opens it is probable that a rough attempt had been made to divide the stars into the groups we call constellations, and to name them, as well as some individual stars. Five bodies—Mercury, Venus, Mars, Jupiter, and Saturnwhich like the sun and moon underwent change of position were called planets, or wanderers, to distinguish them from the so-called fixed stars. One of the first purposes to which astronomy was applied was the measurement of time. The appearance and disappearance of the sun, bringing heat and light, or leaving darkness behind it, is the most obvious of astronomical facts, and thus the day is the simplest unit of time. The next most obvious unit is the lunar month-that is, the period during which the moon goes through her phases. The

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