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the fire, in the warm and ascending air. Others tell us, that it was his brother Joseph who first thought of it, on perceiving the smoke ascending his chimney one day, during the memorable siege of Gibraltar, as he was sitting alone, and musing on the possibility of penetrating into the place, to which his attention had been called at the moment by a picture of it, on which he had accidentally cast his eyes. It is known, however, that the two brothers had, before this, studied and made themselves familiar with Priestley's work on the different kinds of air; and it is even said that Stephen had conceived the idea of navigating the heavens, by the employment of a gas lighter than common atmospheric air, on his way home from Montpelier, where he had purchased that book. Newton, too, is well known to have been indebted for the first hint of certain of his great optical discoveries to the child's amusement of blowing bubbles out of soap; and as Dr. Pemberton has ingeniously observed, in his account of that great man's philosophy, “it is suitably to this mode of thinking that he has, in his Observations on Daniel, made a very curious as well as useful remark, that our Saviour's precepts were all occasioned by some ordinary circumstance of things then especially before him."
Such is the way in which out of a very little matter has not unfrequently grown a large produce of philosophy. Originally, all human knowledge was nothing more than the knowledge of a comparatively small number of such simple facts, as those from which Galileo deduced the use of the pendulum for the measurement of time, and Newton the explanation of the system of the heavens. All the rest of our knowledge, and these first rudiments of it also, a succession of individuals have gradually discovered in separate portions, by their own efforts, and without
having any teacher to instruct them. In other words, every thing that is actually known has been found out and learned by some person or other, without the aid of an instructor. This is the first consideration for all those who aspire, in the present day, to be their own instructors in any branch of science or literature. Furnished as society now is, in all its departments, with accommodations in aid of intellectual exertion, such as, in some respects, even the highest station and the greatest wealth in former times could not command, it may be safely asserted, that hardly any unassisted student can have at present difficulties to encounter, equal to those which have been a thousand times already triumphantly overcome by others. Above all, books, and especially elementary 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 shew. 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 instructors, want of books, poverty, ill health, imprisonment, uncongenial or distracting occupations, the force of opposing example, the discouragement of friends or relations, the depressing consideration 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 situation, in truth, is altogether without its unfavourable influences. If there be not poverty to crush, there may be wealth and ease to relax, the spirit. He who is left to educate himself in every thing, may
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 as any occupation. 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, for all who love to read of bold and succéssful 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.
Strength of the Passion for Knowledge, Pythagoras; Archimedes ;
Leibnitz; Galileo; Heyne.
The ardour with which knowledge has frequently been pursued amidst 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 already 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 ecstasy. 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 to 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