These applications of chemistry have been rendered possible by improved methods of investigation, a greater knowledge of the nature of matter itself, and the perfection of scientific instruments of precision. These instruments are so much finer and more delicate than our senses that they have been the means of disclosing the actual constitution of matter. A man might sit and “meditate” upon the nature of matter for years, but he would be no nearer an actual proof as to its constitution than he was at the beginning. It is generally conceded that Aristotle possessed one of the finest minds the world has ever known; yet any school boy today knows more of the ultimate constitution of matter than did Aristotle. The reason for this is that instrumental methods of research have enabled us to see and measure the ultimate properties of matter,—which our unaided senses would never permit us to do. The development of science in other fields, therefore, has rendered possible the rapid growth of chemistry, during the past century; and chemistry, in turn, has assisted the other sciences. Thus does all knowledge work hand in hand, when co-operation is rendered possible!
SALINITY OF THE OCEANS
I referred some time ago to the calculations which had been made as to the age of the earth, based upon researches as to the salinity of the ocean. As we know, the water of all the oceans is salt water; only that of rivers and lakes is “fresh.” But the degree of the ocean’s saltness is not quite constant. It varies, since evaporation is constantly taking place; sediments are deposited; and above all vast quantities of water are being poured into the ocean by the hundreds of rivers which flow into it, carrying all kinds of earthy deposits which have been washed away by their passage through the river-beds over which they flow.
In 1715, the famous astronomer Edmund Halley published a paper entitled “A Short Account of the Saltness of the Ocean.... With a Proposal by Help Thereof to Discover the Age of the World.” No definite progress was made, however, until 1899, when Joly pointed out that of the many elements which enter into the composition of salt water, sodium alone tends to accumulate. All the others are sooner or later rejected, associating themselves with the detrital sediments, or forming chemical or organic sediments by their ultimate precipitation. He accordingly used sodium as the index of the age of the oceans. He assumed that the annual increase of sodium has been more or less constant, being added to every year by the quantity washed into the ocean by the rivers. How long a period of time would it require to reach its present degree of saltness? Taking all the oceans as one, the volume of the ocean is approximately 320,000,000 cubic miles. Its density (according to Murray) is 1.026. On the basis of these figures, Joly, and after him Sollas and others, calculated that it would require from 80 to 150 million years for the present degree of salinity to be reached. Ninety or a hundred million years would be a fair estimate. Indirectly therefore, the study of the salinity of the oceans has thrown light upon the age of our earth, and its chemical constitution throughout geological ages.
THE NEWER CHEMISTRY
It will be seen, therefore, that chemistry has not only proved of the utmost practical value to mankind, but that it has been instrumental in solving some of the greatest enigmas confronting the mind of man, and in settling some philosophical and even theological questions. (The age of the earth, the composition and habitability of distant stars, etc.) Attempts have been made to account for life itself along purely physico-chemical lines. And all this was attempted—and in part even rendered possible—before the ultimate constitution of matter was known! During the present generation, an entirely new light has been thrown upon this central problem, and the ideas of centuries have been discarded. Let us trace the final steps of research in this direction, and see how the latest findings of modern science have thrown light upon the world-old problem of the ultimate constitution of matter.
RADIO-ACTIVITY
We saw at the very beginning of this little book that, from time immemorial, something corresponding to Atoms were regarded as the ultimate “building stones” of the universe—tiny particles, incapable of diversion, beyond which it was impossible to go. Beginning with Epicurus and Democritus, this idea took scientific form; it was held by many philosophers throughout the ages; it formed the basis of Dalton’s atomic theory, and was assumed by the Periodic Law. It was not until the last years of the preceding century that this idea was called into question. The discovery of radium, by the Curies, caused a sensation in the scientific world. How account for the phenomena observed? Radium seemed to give off energy continuously, without losing any; heat was constantly being radiated without lessening the original amount. Had the secret of perpetual motion been discovered? What was happening? The discovery of other radio-active elements only tended to increase the problem, instead of solving it. Here was some new property of matter, hitherto unsuspected, going on before the eyes of chemists, which they could not understand or explain.
INTRA-ATOMIC ENERGY
Professor E. Rutherford, of M’Gill University, Canada, was among the first to propose a new and startling theory. He said: Suppose that the atoms are not indivisible? Suppose that they are capable of being split-up into something still smaller and finer? If the atoms themselves are being disintegrated, immense quantities of energy would probably be available—“intra-atomic energy”—which would account for the results obtained. It is true that we should no longer have our stable atoms; they would vanish and be represented by something else. And that “something” would no longer be matter, in the sense that we now understand it; but we could account for the observed facts (radio-activity, etc.), and we can then endeavor to discover what atoms are resolved into later on. This theory was soon proved to be true; atoms were shown to be divisible, and capable of being split-up into something still smaller, which were no longer “matter” in the old sense. Matter, in short, had technically disappeared, and had been resolved into its component parts. This being so, the question at once arose: Of what is matter (the atom) composed?