advantage of his fellow-men, and to the immediate advancement of his country's welfare, that he earned his chief title to be remembered with admiration and gratitude by the great mass of mankind.

It must be acknowledged, however, at the outset, that there is too much reason for supposing, that most of what he did in this way was prompted by but little feeling of personal respect for anything of practical art, and by but little original impulse of philanthropy. He lived at a day when it was not thought quite consistent with the dignity of a philosopher to busy himself with any of the common affairs or common interests of society. Plutarch tells us, that "the first that turned their thoughts to Mechanics, a branch of knowledge which came afterwards to be so much admired, were Eudoxus and Archytas, who thus gave a variety and an agreeable turn to Geometry, and confirmed certain problems by sensible experiments and the use of instruments, which could not be demonstrated in the way of theorem." "But," he adds, "when Plato inveighed against them with great indignation, as corrupting and debasing the excellence of Geometry, by making her descend from incorporeal and intellectual to corporeal and sensible things, and by thus obliging her to make use of matter, which requires much manual labor and is the object of servile trades, then Mechanics were separated from Geometry, and being a long time despised by the philosophers, were considered only as a branch of the military art."

In another place, in speaking of some of the great machines which Archimedes invented, he says, "Yet Archimedes had such a depth of understanding, such a dignity of sentiment, and so copious a fund of mathematical knowledge, that though in the invention of these machines he gained the reputation of a man endowed with divine rather than human knowledge, yet he did not

vouchsafe to leave behind him any account of them in writing. For he considered all attention to Mechanics, and every art that ministers to common uses, as mean and sordid, and placed his whole delight in those intellectual speculations, which, without any relation to the necessities of life, have an intrinsic excellence arising from truth and demonstration only."

The old Greek biographer, indeed, seems disposed even to apologize for the great Geometrician, by representing him, in his mechanical inventions, as yielding reluctantly to the importunity of his royal relative. "He did not think the inventing of them (says he) an object worthy of his serious studies, but only reckoned them among the amusements of Geometry. Nor had he gone so far, but at the pressing instance of King Hiero, who entreated him to turn his art from abstracted notions to matters of sense, and to make his reasonings more intelligible to the generality of mankind by applying them to the uses of common life."

Thus, according to Plutarch's account, it is King Hiero, who deserves the credit of having originally prompted that "application of Science to Art," which is to be the subject of your Lectures, and which is the great secret and source of the wonderful inventions and improvements of modern times. And a brave and noble fellow this Hiero certainly was,-Hiero the Second, King of Syracuse,-who, during a reign of more than half a century, devoted himself to promoting the arts of peace, adorning the city over which he reigned with numberless works of public utility as well as of great magnificence, while he ruled his people with an almost republican simplicity, and with much of the substance, and not a few of the forms, of a free constitutional government. A modern commentator on the character of Archimedes * seems to think that Plutarch "confounded the

Professor Donkin of Oxford.

application of geometry to mechanics with the solution of geometrical problems by mechanical means," and that he is mistaken in representing Archimedes as despising all mechanical contrivances and practical inventions. I would gladly believe that this is a true theory, but I confess to a good deal of distrust for these corrections of history eighteen hundred years after it was written, and in regard to points, too, upon which no new facts or new testimony have been, or can be, procured.

But whatever may have been the circumstances under which Archimedes originally turned his mind and his hand to mechanical inventions, and in whatever estimation he may himself have held the practical arts and sciences, the noble use to which he afterwards applied them, no less than the wonderful effects which he afterwards produced with them, will be enough to secure him an everlasting remembrance among men.

There is no more characteristic anecdote of this great philosopher, than that relating to his detection of a fraud in the composition of the royal crown. Nothing, certainly, could more vividly illustrate the ingenuity, the enthusiasm, and the complete concentration and abstraction of mind with which he pursued whatever problem was proposed to him.

King Hiero, or his son Gelon, it seems, had given out a certain amount of gold to be made into a crown, and the workman to whom it had been intrusted, had at last brought back a crown of corresponding weight. But a suspicion arose that it had been alloyed with silver, and Archimedes was applied to by the King, either to disprove or to verify the allegation. The great problem, of course, was to ascertain the precise bulk of the crown in its existing form; for gold being so much heavier than silver, it is obvious that if the weight had been in any degree made up by the substitution of silver, the bulk would be proportionately increased. Now it happened that Archim

edes went to take a bath, while this problem was exercising his mind, and, on approaching the bath-tub, he found it full to the very brim. It instantly occurred to him, that a quantity of water of the same bulk with his own body must be displaced before his body could be immersed. Accordingly, he plunged in; and while the process of displacement was going on, and the water was running out, the idea suggested itself to him, that by putting a lump of gold of the exact weight of the crown into a vessel full of water, and then measuring the water which was displaced by it, and by afterwards putting the crown itself into the same vessel after it had again been filled, and then measuring the water which this, too, should have displaced, the difference in their respective bulks, however minute, would be at once detected, and the fraud exposed. "As soon as he had hit upon this method of detection, (we are told,) he did not wait a moment, but jumped joyfully out of the bath, and running naked towards his own house, called out with a loud voice that he had found what he had sought. For, as he run, he called out in Greek, 'Eureka, Eureka.'"

No wonder that this veteran Geometer, rushing through the thronged and splendid streets of Syracuse, naked as a pair of his own compasses, and making the welkin ring with his triumphant shouts,-no wonder that he should have rendered the phrase, if not the guise, in which he announced his success, familiar to all the world, and that "Eureka, Eureka," should thus have become the proverbial ejaculation of successful invention and discovery in all ages and in all languages from that day to this!

The solution of this problem is supposed to have led the old philosopher not merely into this ecstatical exhibition of himself, but into that entire line of hydrostatical investigation and experiment, which afterwards secured him such lasting renown. And thus the accidents of a

defective crown and an overflowing bath-tub, gave occasion to some of the most remarkable demonstrations of ancient science.

At the instigation and under the auspices of this same King Hiero, Archimedes achieved another of his memorable triumphs, in the building of a ship of wonderful dimensions, far exceeding anything which had ever before been constructed; and which, if the accounts of its magnitude and its magnificence, of its banqueting rooms, and galleries, and stables, -its baths, its fishponds, its temple of Venus, and its floors inlaid with scenes from Homer's Iliad,-be not greatly exaggerated, must have been a perfect floating city of itself, and must have been more than a match, in splendor and in size, if not in speed, even for the Great Republic of our worthy friend and fellow-citizen, Donald McKay.*

One might imagine that it was from the accounts which have come down to us of this marvelous vessel, that Shakspeare,-who, though he is said to have "had small Latin and less Greek," yet always contrived to pick up whatever either Greek or Latin authors contained which could serve his turn and adorn his story or his style, must have derived the idea of that gorgeous bark in which he represents Cleopatra-the serpent of old Nile-sailing down the Cydnus to make captive of the valiant but voluptuous Anthony:

"The barge she sat in, like a burnished throne,
Burned on the water; the poop was beaten gold;
Purple the sails, and so perfumed, that

The winds were love-sick with them; the oars were silver,
Which to the tune of flutes kept stroke."

*While this Lecture is going through the press, the telegraph informs us that the Great Republic has been burned to the water's edge at New York. Every one will sympathize with Donald McKay in this sad disappointment, and will deeply regret that so noble a specimen of naval architecture should have met with so untimely a fate.