books, have, in our day, been multiplied to an extent that puts them within the reach almost of the poorest student; and books, after all, are, at least to the more mature understanding, and in regard to such subjects as they are fitted to explain, the best teachers. He who can read, and is possessed of a good elementary treatise on the science he wishes to learn, hardly, in truth, needs a master. With only this assistance, and sometimes with hardly this, some of the greatest scholars and philosophers that ever appeared have formed themselves, as the following pages will show. And let him who, smitten by the love of knowledge, may yet conceive himself to be on any account unfortunately circumstanced for the business of mental cultivation, bethink him how often the eager student has triumphed over a host of impediments, much more formidable in all probability than any by which he is surrounded. Want of leisure, want of instructers, want of books, poverty, ill health, imprisonment, uncongenial or distracting occupations, the force of opposing example, the discouragement of friends or relatives, the depressing considerations that the better part of life was already spent and gone-these have all, separately or in various combinations, exerted their influence either to check the pursuit of knowledge, or to prevent the very desire of it from springing up. But they exerted this influence in vain. Here, then is, enough both of encouragement and of direction for all. To the illustrious vanquishers of fortune, whose triumphs we are about to record, we would point as guides for all who, similarly circumstanced, may aspire to follow in the same honourable path. Their lives are lessons that cannot be read without profit, nor are they lessons for the perusal of one class of society only. All, even those who are seemingly the most happily situated for the cultivation of their minds, may derive a stimulus from such anecdotes. No situa

tion, in truth, is altogether without its unfavourable influences. If there be no poverty to crush, there may be wealth and ease to relax the spirit. He who is left to educate himself in everything, may have many difficulties to struggle with; but he who is saved every struggle is perhaps still more unfortunate. If one mind be in danger of starving for want of books, another may be surfeited by too many. If, again, a laborious occupation leave to some but little time for study, there are temptations, it should be remembered, attendant upon rank and affluence, which are to the full as hard to escape from. If, however, there be any one who stands free, or comparatively free, from every kind of impediment to the cultivation of his intellectual faculties, surely he must peruse with peculiar interest the account of what the love of knowledge has achieved in circumstances so opposite to his own. Certain, at least, it is, that such achievements produce a most powerful call upon his exertions in the pursuit of science and literature, that his acquisitions may be in some degree commensurate to his advantages. Finally, to all who love to read of bold and successful adventure, and to follow daring ambition in its career to greatness, it cannot but be interesting to contemplate the exploits of some of the most enterprising spirits of our race; the adventurers, namely, of the world of intellect, whose ambition, while it has soared as high, and performed feats as brilliant as any other, never excites in us an interest dangerous to feel, nor holds up to us an example criminal to follow; because its conquests have been a blessing, and not a curse, to humanity,

CHAPTER II.

Strength of the Passion for Knowledge. Pythagoras; Archimedes; Erasmus; Kepler; Magliabechi; Heyne.

THE ardour with which knowledge has frequently been pursued amid all sorts of difficulties and discouragements, is the best evidence we can offer of the strength of the passion which has sprung up and lived in circumstances so unfavourable to its growth, and, therefore, of the exquisite pleasure, which its gratification is found to bring with it. If the permanence of any pleasure, indeed, is to be looked upon as one of the proofs of its value, there are certainly none but those of virtue and religion that can be compared with the pleasures of intellectual exertion. Nor is successful study without its moments, too, of as keen and overpowering emotion, as any other species of human enjoyment is capable of yielding. We have seen how Newton was affected on approaching the completion of his sublime discovery; when the truth shone full upon him, and not a shade remained to create a doubt that it was indeed the truth which he had found and upon which he was gazing. Every other discoverer, or inventor, or creator of any of the great works of literature or art, has had, doubtless, his moments of similar ecstacy. The ancient Greek philosopher, PYTHAGORAS, is said to have been the first who found out, or at least demonstrated, the great geometrical truth, that the square described on the hypothenuse, or side opposite the right angle of a right-angled triangle, is exactly equal in area to the two squares described on the other two sides; and such was his joy, we are told, on the occasion, that he offered up a hecatomb,

or sacrifice of a hundred oxen, to the gods, in testimony of his gratitude and exultation.

"The proposition in Hydrostatics, that a solid plunged in a fluid displaces a quantity of the fluid equal to its bulk, was discovered by ARCHIMEDES, one of the greatest mathematicians of ancient times, in consequence of Hiero, king of Syracuse, his friend and patron, and himself an eminent philosopher, and, it needs hardly be added, a virtuous and patriotic prince, having set him a problem to solve upon the adulteration of metals. Hiero had given a certain quantity of gold to an artist to make into a crown, and suspecting, from the lightness of the crown, that some silver had been used in making it, he begged Archimedes to investigate the matter. It is said that while this great man was intent upon the question, he chanced to observe, in bathing, the water which ran over the sides of the bath; and immediately perceiving that, as the water was equal to the bulk of his body, this would furnish him with the means of detecting the adulteration, by trying how much water a certain weight of silver displaced, how much a certain weight of gold, and how much a certain mixture of the two, he rushed out of the chamber, exclaiming, 'I have found it! I have found it!"

But beyond all, perhaps, that a discoverer ever felt, must have been the surprise and delight of Galileo, when, having turned for the first time to the heavens the wonderful instrument which his own ingenuity had invented, he beheld that crowd of splendours which had never before revealed themselves to the eye, nor even been dreamed of by the imagination of man. While Galileo resided at Venice, a report was brought to that city that a Dutchman had presented to Count Maurice of Nassau an instrument, by means of which distant objects were made to appear as if they were near; and this was all that the rumour stated. But it was

enough for Galileo. The philosopher immediately set himself to work to find out by what means the thing must have been effected; and, in the course of a few hours, satisfied himself that, by a certain arrangement of spherical glasses, he could repeat the new miracle. In the course of two or three days he presented several telescopes to the Senate of Venice, accompanied with a memoir on the immense importance of the instrument to science, and especially to astronomy. He afterward greatly improved his invention; and brought it to such a state of perfection, that he was in a condition to commence, by means of it, the examination of the heavens. It was then that, to his unutterable astonishment, he saw, as a celebrated French astronomer has expressed it, "what no mortal. before that moment had seen-the surface of the moon, like another earth, ridged by high mountains, and furrowed by deep valleys-Venus, as well as it, presenting phases demonstrative of a spherical form; Jupiter surrounded by four satellites, which accompanied him in his orbit; the milkyway; the nebulæ; finally, the whole heaven sown over with an infinite multitude of stars, too small to be discerned by the naked eye." From this period the examination of the heavens became the sole object of Galileo's thoughts and the occupation of his life. He wrote, he talked of nothing else.

Every mind which is yet a stranger to science, is, in some respects, in the same situation with that of Galileo, before he turned his telescope to the heavens; and such a mind has a world of wonders to learn, many of which are as extraordinary as those which then revealed themselves to the philosopher. It has, in fact, to behold all that he beheld; not certainly, like him, for the first time that any one of the human race had been admitted to that high privilege, but yet for the first time, too,