26

THE MEASUREMENT OF THE EARTH.

is called the Square Porch,"-probably somewhere in the Museum. By these he had calculated the obliquity of the ecliptic, closely enough to serve for a thousand years after. That was one work done. But what had the Syene shadows to do with that? Syene must be under that ecliptic. On the edge of it. In short, just under the tropic. Now he had ascertained exactly the latitude of one place on the earth's surface. He had his known point from whence to start on a worldjourney, and he would use it; he would calculate the circumference of the earth, and he did it. By observations made at Alexandria, he ascertained its latitude compared with that of Syene; and so ascertained what proportion to the whole circumference was borne by the 5,000 stadia between Alexandria and Syene. He fell into an error, by supposing Alexandria and Syene to be under the same meridians of longitude: but that did not prevent his arriving at a fair rough result of 252,000 stadia,-31,500 Roman miles; considerably too much; but still, before him, I suppose, none knew whether it was 10,000, or 10,000,000. The right method having once been found, nothing remained but to employ it more accurately.

One other great merit of Eratosthenes is, that he first raised Geography to the rank of a science. His Geographica were an organic collection, the first the world had ever seen, of all the travels and books of earth-description heaped together in the Great Library, of which he was for many years the keeper. He began with a geognostic book, touched on the traces of Cataclysms and Change, visible on the earth's surface; followed by two books, one a mathematic book, the other on political geography, and completed by a mapwhich one would like to see: but not a trace of all remains, but a few quoted fragments—

"We are such stuff

As dreams are made of."

But if Eratosthenes had hold of eternal fact and law on one point, there was a contemporary who had hold of it in more than one. I mean Archimedes; of whom, as I have said, we must speak as of an Alexandrian. It was as a mechanician, rather than as an astronomer, that he gained his reputation. The stories of his Hydraulic Screw, the Great Ship which he built for Hiero, and launched by means of machinery, his crane, his war-engines, above all his somewhat mythical arrangement of mirrors,

28

ARISTOTLE ON THE LEVER.

by which he set fire to ships in the harbour-all these, like the story of his detecting the alloy in Hiero's crown, while he himself was in the bath, and running home undressed shouting evρnkaall these are schoolboys' tales. To the thoughtful person it is the method of the man which constitutes his real greatness, that power of insight by which he solved the two great problems of the nature of the lever and of hydrostatic pressure, which form the basis of all static and hydrostatic science to this day. And yet on that very question of the lever the great mind of Aristotle babbles-neither sees the thing itself, nor the way towards seeing it. And since Archimedes spoke, the thing seems selfevident to every schoolboy. There is something to me very solemn in such a fact as this. It brings us down to some of the very deepest questions of metaphysic. This mental insight of which we boast so much, what is it? Is it altogether a process of our own brain and will? If it be, why have so few the power, even among men of power, and they so seldom? If brain alone were what was wanted, what could not Aristotle have discovered? Or is it that no man can see a thing unless God shows it him?

WHAT IS INDUCTION?

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Is it that in each separate act of induction, that mysterious and transcendental process which cannot, let logicians try as they will, be expressed by any merely logical formula, Aristotelian or other-is it, I say, that in each separate act of induction we do not find the law, but the law is shown to us, by Him who made the law? Bacon thought so. Of that you

may find clear proof in his writings. May not Bacon be right? May it not be true that God does in science, as well as in ethics, hide things from the wise and prudent, from the proud, complete, self-contained systematizer like Aristotle, who must needs explain all things in heaven and earth by his own formulæ, and his entelechies and energies, and the rest of the notions which he has made for himself out of his own brain, and then pack each thing away in its proper niche in his great cloud-universe of conceptions? Is it that God hides things from such men many a time, and reveals them to babes, to gentle, affectionate, simple-hearted men, such as we know Archimedes to have been, who do not try to give an explanation for a fact, but feel how awful and divine it is, and wrestle reverently and stedfastly with it, as Jacob with the Angel, and will not let it go, until it bless them? Sure I am,

from what I have seen of scientific men, that there is an intimate connexion between the health of the moral faculties and the health of the inductive ones; and that the proud, self-conceited, and passionate man will see nothing: perhaps because nothing will be shown him.

But we must leave Archimedes for a man not perhaps so well known, but to whom we owe as much, as to the great Syracusan;-Hipparchus the astronomer. To his case much which I have just said applies. In him astronomic science seemed to awaken suddenly to a true inductive method, and after him to fall into its old slumber for 300 years. In the meantime Timocharis, Aristyllus and Conon had each added their mites to the discoveries of Eratosthenes: but to Hipparchus we owe that theory of the heavens, commonly called the Ptolemaic system, which starting from the assumption that the earth was the centre of the universe, attempted to explain the motions of the heavenly bodies by a complex system of supposed eccentrics and epicyles. This has of course now vanished before modern discoveries. But its value as a scientific attempt lies in this that the method being a correct one, correct results were obtained, though starting from a false assumption; and Hipparchus and

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