Imagens das páginas
PDF
ePub

THE NEW CHEMISTRY.

LECTURE I.

MOLECULES AND AVOGADRO'S LAW.

In every physical science we have carefully to distinguish between the facts which form its subject-matter and the theories by which we attempt to explain these facts, and group them in our scientific systems. The first alone can be regarded as absolute knowledge, and such knowledge is immutable, except in so far as subsequent observation may correct previous error. The last are, at best, only guesses at truth, and, even in their highest development, are subject to limitations, and liable to change.

But this distinction, so obvious when stated, is often overlooked in our scientific text books, and not without reason, for it is the sole aim of these elementary treatises to teach the present state of knowledge, and they might fail in their object if they attempted, by a too critical analysis, to separate the phenomena from the systems by which alone the facts of Nature are correlated and rendered intelligible.

When, however, we come to study the history of science, the distinction between fact and theory obtrudes itself at once upon our attention. We see that, while the prominent facts of science have re

mained the same, its history has been marked by very frequent revolutions in its theories or systems. The courses of the planets have not changed since they were watched by the Chaldean astronomers, three thousand years ago; but how differently have their motions been explained-first by Hipparchus and Ptolemy, then by Copernicus and Kepler, and lastly by Newton and Laplace!—and, however great our faith in the law of universal gravitation, it is difficult to believe that even this grand generalization is the final result of astronomical science.

Let me not, however, be understood to imply a belief that man cannot attain to any absolute scientific truth; for I believe that he can, and I feel that every great generalization brings him a step nearer to the promised goal. Moreover, I sympathize with that beautiful idea of Oersted, which he expressed in the now familiar phrase, "The laws of Nature are the thoughts of God;" but, then, I also know that our knowledge of these laws is as yet very imperfect, and that our human systems must be at the best but very partial expressions of the truth. Still, it is a fact, worthy of our profound attention, that in each of the physical sciences, as in astronomy, the successive great generalizations which have marked its progress have included and expanded rather than superseded those which went before them. Through the great revolutions which have taken place in the forms of thought, the elements of truth in the successive systems have been preserved, while the error has been as constantly eliminated; and so, as I believe, it always will be, until the last generalization of all brings us into the presence of that law which is indeed the thought of God.

There is also another fact, which has an important

ANTICIPATION IN SCIENCE.

11

bearing on the subject we are considering. Almost all the great generalizations of science have been more or less fully anticipated, at least in so far that the general truth which they involve has been previously conceived. The Copernican theory was taught, substantially, by the disciples of Pythagoras. The law of gravitation was suggested, both by Hooke and Cassini, several years before Newton published his “Principia;” and the same general fact has been recently very markedly illustrated in the discovery of the methods of spectrum analysis, every principle of which had been previously announced. The history of science shows that the age must be prepared before really new scientific truths can take root and grow. The barren premonitions of science have been barren because these seeds of truth fell upon unfruitful soil; and, as soon as the fullness of the time was come, the seed has taken root and the fruit has ripened. No one can doubt, for example, that the law of gravitation would have been discovered before the close of the seventeenth century if Newton had not lived; and it is equally true that, had Newton lived before Galileo and Kepler, he never could have mastered the difficult problems it was his privilege to solve. We justly honor with the greatest veneration the true men who, having been called to occupy these distinguished places in the history of science, have been equal to their position, and have acquitted themselves so nobly before the world; but every student is surprised to find how very little is the share of new truth which even the greatest genius has added to the previous stock. Science is a growth of time, and, though man's cultivation of the field is an essential condition of that growth, the development steadily progresses, independently of any in

dividual investigator, however great his mental power. The greatest philosophical generalizations, if premature, will fall on barren soil, and, when the age is ripe, they are never long delayed. The very discovery of law is regulated by law, or, as we rather believe, is directed by Providence; but, however we may prefer to represent the facts, this natural growth of knowledge gives us the strongest assurance that the growth is sound and the progress real. Although the foundations of science have been laid in such obscurity, its students have worked under the direction of the same guiding power which rules over the whole of Nature, and it cannot be that the structure they have reared with so much care is nothing but the phantom of a dream. Still it is true that, beyond the limits of direct observation, our science is not infallible, and our theories and systems, although they may all contain a kernel of truth, undergo frequent changes, and are often revolutionized.

Through such a revolution the theory of chemistry has recently passed, and the system which is now universally accepted by the principal students of the science is greatly different from that which has been taught in our schools and colleges until within a few years. I have, therefore, felt that the best service I could render in this course of lectures would be to explain, as clearly as I am able, the principles on which the new philosophy is based, and to show in what it differs from the old. I have felt that there were many who, having studied what we must now call the old chemistry, would be glad to bridge over the gulf which separates it from the new, and to become acquainted with the methods by which we now seek to group together and explain the old facts.

« AnteriorContinuar »