Page images
PDF
EPUB

would strongly urge young men who listen to lectures to

PREFACE.

The present is the fourth volume of the “POPULAR LECTURER,” new series. It contains 30 lectures, extending to 354 pages, the average cost being one penny each. The subjects treated comprise Education, Natural History, Language, Mechanics, Industry, Cotton, Pictures, Travels, Biography, Mining, Science, Poetry, Music, &c.

Amongst the authors of these lectures will be found the names of Lord Brougham; the Rev. Dr. Hook;

Dr. Latham; the Dean of Carlisle ; Thomas Bazley, Esq., M.P.; Leo. H. Grindon, Esq. ; R. W. Emerson, Esq.; the Rev. Marmaduke Miller; George Dawson, Esq.,

M.A. ; His Royal Highness the Prince Consort; E. W. Binney, Esq., F. R.S., F.G.S. ; the Right Hon. Sir James Stephen ; and other well-known naines in literature and science.

The volume will be found to contain a large fund of valuable and interesting information, of the kind most serviceable to students, and the members of educational institutions generally. A “revival” is taking place in the art of lecturing, and our readers shall have the benefit of it. We

study shorthand. Phonography is the system in which

these lectures have been reported by

THE EDITOR.

its expansion has the same happy effect naturally of preventing mischief from its excess, which the skill of the great mechanist gave artificially to steam, thus rendering his engine as safe as it is powerful.

The grand difference, then, between one discovery or invention and another, is in degree, rather than in kind; the degree in which a person, while he outstrips those whom he comes after, also lives, as it were, before his age. Nor can any doubt exist that, in this respect, Newton stands at the head of all who have extended the bounds of knowledge. The sciences of dynamics and of optics are especially to be regarded in this point of view; but the former in particular; and the completeness of the system which ħe unfolded,,its having been at the first elaborated and given in perfection,-—its having, however new, stood the test of time, and survived, nay gained by, the most rigorous scrutiny—can be predicated of this system alone, at least in the same degree. That the calculus, and those parts of dynamics which are purely mathematical, should thus endure for ever, is a matter of course. But his system of the universe rests partly upon contingent truths, and might have yielded to new experiments and more extended observation. Nay, at times it has been thought to fail, and further investigation was deemed requisite to ascertain if any error had been introduced-if any circumstance had escaped the notice of the great founder. The most memorable instance of this kind is the discrepancy supposed to have been found between the theory and the fact in the motion of the lunar apsides, which about the middle of the last century occupied the three first analysts of the age. The error was discovered by themselves to have been their own in the process of their investigation; and this, like all the other doubts that were ever momentarily entertained, only led in each instance to new and more brilliant triumphs of the system. The prodigious superiority in this cardinal point of the

[ocr errors]

Newtonian to other discoveries, appears manifest upon
examining almost any of the chapters in the history
of science. Successive improvements have, by ex-
tending our views, constantly displaced the system
that appeared firmly established. To take a familiar
instance, how little remains of Lavoisier's doctrine
of combustion and acidification, except the negative
positions, the subversion of the system of Stahl. The
substance having most eminently the properties of
an acid (chlorine) is found to have no oxygen at all,
while many substances abounding in oxygen, includ-
ing alkalis themselves, have no acid property what-
ever; and without the access of oxygenous or of any
other gas, heat and flame are produced in excess.

The doctrines of free trade had not long been promulgated by Smith, before Bentham demonstrated that his exception of usury was groundless; and his theory has been repeatedly proved erroneous on colonial establishments, as well as his exception to it on the navigation laws; and the imperfection of his views on the nature of rent is undeniable, as well as on the principle of population. In these, and such instances as these, it would not be easy to find in the original doctrines the means of correcting subsequent errors, or the germs of extended discovery. But even if philosophers finally adopt the undulatory theory of light, instead of the atomic, it must be borne in mind that Newton gave the first elements of it by the well-known proposition in the 8th section of the Second Book of the Principia, the scholium to that section also indicating his expectation that it would be applied to optical science; wbile M. Brot has shown how the doctrine of fits of reflection and transmission tallies with polarization, if not with undulation also. But the most marvellous attribute of Newton's discoveries, is that in which they stand out prominent among all the other feats of scientific research, stamped with the peculiarity of his intellectual character; they were, their great author lived,

1

ness.

before his age, anticipating in part what was long after wholly accomplished, and thus unfolding some things which at the time could be but imperfectly, others not at all, comprehended; and not rarely pointing out the path and affording the means of treading it, to the ascertainment of truths then veiled in dark

He not only enlarged the actual dominion of knowledge, penetrating to regions never before explored, and taking with a firm hand indisputable possession; but he showed how the bounds of the visible horizon might be yet further extended, and enabled his successors to occupy what he could only descry; as the illustrious discoverer of the new world made the inhabitants of the old cast their eyes over lands and seas for distant from those he had traversed; lands and seas which they could form to themselves no conception of, any more than they had been able to comprehend the course by which he led them on his grand enterprise. In this achievement, and in the qualities which alone made it possible, inexhaustible fertility of resources, patience unsubdued, close meditation that would suffer no distraction, steady determination to pursue paths that seemed all but hopeless, and unflinching courage to declare the truths they led to, how far soever removed from ordinary apprehension,-in these characteristics of high and original genius, we may be permitted to compare the career of those great men. But Columbus did not invent the mariner's compass, as Newton did the instrument which guided his course and enabled him to make his discoveries, and his successors to extend them by closely following his directions in using it. Nor did the compass suffice to the great navigator without making any observations, though he dared to steer without a chart; while it is certain that by the philosopher's instrument his discoveries were extended over the whole system of the universe, deterniining the masses, the forms, and the motions of all its parts, by the mere inspection of abstract calculations and formulas analytically deduced.

The two great improvements in this instrument which have been made—the calculus of variations by Euler and La Grange, the method of partial differences by d'Alembert-we have every reason to believe were known, at least in part, to Newton himself. His having solved an isoperimetrical problem (finding the line whose revolution forms the solid of least resistance), shows clearly that he must have made the co-ordinates of the generating curve vary; and his construction agrees exactly with the equation given by that calculus. That he must have tried the process of integrating by parts in attempting to generalize the inverse problem of central forces, before he had recourse to the geometrical approximation which he has given, and also when he sought the means of ascertaining the comet's path, which he has termed by far the most difficult of problems, is eminently probable, when we consider how naturally that method flows from the ordinary process for differentiating compound quantities, by supposing each variable in succession constant; in short, differentiating by parts. As to the calculus of variations having substantially been known to him, no doubt can be entertained. Again, in estimating the ellipticity of the earth, he proceeded upon the assumption of a proposition of which he gave no demonstration (any more than he had done of the isoperimetrical problem) that the ratio of the centrifugal force to gravitation determines the ellipticity. Half a century later, that which no one before knew to be true, which many probably considered to be Erroneous, was examined by one of his most distinguished followers, Maclaurin, and demonstrated most satisfactorily to be true. Newton had not failed to perceive the necessary effects of gravitation in producing other phenomena, beside the regular motion of the planets and their satellites in their course round their several centres of attraction. One of these phenonema, wholly unsuspected before the

« EelmineJätka »