THE

PURSUIT OF KNOWLEDGE,

ILLUSTRATED BY

NOTICES OF REMARKABLE MEN.

CHAPTER I.

Introduction. Newton; Galileo; Torricelli; Pascal; Self-ed ucation.

We are about to select from the records of Philosophy, Literature, and Art, in all ages and countries, a body of examples, to show how the most unpropitious circumstances have been unable to conquer an ardent desire for the acquisition of knowledge. Every man has difficulties to encounter in this pursuit, and therefore every man is interested in learning what are the obstacles which have opposed themselves to the progress of some of the most distinguished persons, and how those obstacles have been surmounted.

The love of knowledge will of itself do a great deal towards its acquisition; and where it exists with that force and constancy which it exhibits in the characters of all truly great men, it will induce that ardent, but humble spirit of observation and inquiry, without which there can be no success. ISAAC NEWTON, of all men that ever lived, is the one

Sir

who has most extended the territory of human knowledge; and still he used to speak of himself as having been all his life but "a child gathering pebbles on the seashore;" meaning probably by that allusion, not only to express his modest conviction how mere an outskirt the field of his discoveries was, compared with the vastness of universal nature, but to describe likewise the spirit in which he had pursued his investigations. That was a spirit, not of selection and system-building, but of childlike alacrity in seizing upon whatever contributions of knowledge Nature threw at his feet, and of submission to all the intimations of observation and experiment. On some occasions he was wont to say, that if there were any mental habit or endowment in which he excelled the generality of men, it was that of patience in the examination of the facts and phenomena of his subject. Other speculators had consulted the book of nature principally for the purpose of seeking in it the defence of some favourite theory; partially, therefore, and hastily, as one would consult a dictionary: Newton perused it as a volume altogether worthy of being studied for its own sake. Hence proceeded both the patience with which he traced its characters, and the rich and plentiful discoveries with which the search rewarded him. If he afterward classified and systematized his knowledge like a philosopher, he had first, to use his own language, gathered it like a child.

It is, indeed, most instructive to all who are anxious to engage in the pursuit of knowledge (and is therefore properly introductory to the general subject we are about to treat), to consider the manner in which both this great man and many others, possessing a portion of his observant and inventive genius, have availed themselves, for the enlargement of the boundaries of philosophy, of such common occurrences as, from their very commonness, had

escaped the attention of all less active and original minds.

Of all sorts of observation, that which exhibits the most penetrating and watchful philosophy is when, out of the facts and incidents of every-day experience, a gifted mind extracts new and important truths, simply by its new manner of looking at them. From one of these simple incidents did Sir Isaac Newton read to the world, for the first time, the system of the universe. It was in the twenty-third year of his age that this extraordinary man was sitting, as we are told, one day in his garden, when an apple fell from a tree beside him. His mind was perhaps occupied, at that fortunate moment, in one of those philosophical speculations on space and motion which are known, about this time, to have engaged much of his attention; and the little incident which interrupted him was instantly seized upon by his eager spirit, and, by that power which is in genius, assimilated with his thoughts. The existence of gravitation, or a tendency to fall towards the centre of the earth, was already known, as affecting all bodies in the immediate vicinity of our planet; and the great Galileo had even ascertained the law, or rate, according to which their motion is accelerated as they continue their descent. But no one had yet dreamed of the gravitation of the heavenly bodies till the idea now first dimly rose in the mind of Newton. The same power, he said to himself, which has drawn this apple from its branch, would have drawn it from a position a thousand times as high. Wherever we go, we find this gravitation reigning over all things. If we ascend even to the top of the highest mountains, we discover no sensible diminution of its power. Why may not its influence extend far beyond any height to which we can make our way? Why may it not reach to the moon itself? Why may not this be the very power which retains that planet in its orbit, and keeps it

revolving as it does around our earth? It was a splendid conjecture, and we may be sure that Newton instantly set all his sagacity at work to verify it. And if the moon, he further considered, be retained in her orbit by a gravitation towards the earth, it is in the highest degree probable that the earth itself, and the other planets which revolve around the sun, are, in like manner, retained in their orbits by a similar tendency towards their central and ruling luminary. Proceeding then, in the mean time, upon this supposition, he found by calculation, and by comparing the periods of the several planets and their distances from the sun, that, if they were really held in their courses by the power of gravity, that power must decrease in a certain proportion, according to the distance of the body upon which it operated. This result he had already anticipated from the consideration that, although we could not detect any such diminution within the comparatively small distance to which our experience was limited, the fact was yet consistent with the whole analogy of nature. Supposing, then, this power, when extended to the moon, to decrease at the same rate at which it appeared to do in regard to the planets which revolved around the sun, he next set himself to calculate whether its force, at such a distance from the earth, would in reality be sufficient to retain that satellite in its orbit, and to account for its known rate of motion. Now this step of the discovery was marked by a very singular circumstance, and one strikingly illustrative of the truly philosophic character of this great man's mind. In the computations which he undertook for the purpose of this investigation, he naturally adopted the common estimate of the magnitude of the earth at that time in use among our geographers and seamen. Indeed, no other then existed for him to adopt still it was even then known to scientific men that this estimate was loose and inaccurate

In fact, it allowed only sixty English miles to a degree of latitude, instead of sixty-nine and a half, which is the true measurement. The consequence was, that the calculation did not answer; it indicated a force of gravity in the moon towards the earth, less by one-sixth than that which was necessary to give the rate of motion actually possessed by that satellite. Another might have thought this but a trifling discrepance, and, in such circumstances, have taxed his ingenuity to account for it in a variety of ways, so as still to save the beautiful and magnificent theory which it came so unseasonably to demolish. But Newton was too true a philosopher, too single-hearted a lover of truth, for this. In his mind, the refutation was complete, and it was so admitted at once. He had made his calculation with care, although one of its elements was false; it did not present the result it ought, had his hypothesis been as true as it was brilliant; and, in his own estimation, he was no longer the discoverer of the secret mechanism of the heavens. By an act of self-denial, more heroic than any other recorded in the annals of intellectual pursuit, he dismissed the whole speculation from his mind, even for years We need hardly state how gloriously this sacrifice was in due time rewarded. By thus keeping his mind unbiased, he was eventually enabled to verify all, and more than all, he had originally suspected. No other speculator had yet followed him in the same path of conjecture; when, a few years after, upon obtaining more correct data, he repeated his calculation, and found it terminate in the very result he had formerly anticipated. The triumph and delight of that moment can hardly be conceived, when he saw at last that the mighty discovery was indeed all his own! It is said that such was his agitation as he proceeded, and perceived every figure bringing him nearer to the object of his hopes, that he was at last actually unable to continue the operation,