The metal Gallium was discovered in 1875 by spectroscopic means. Its properties are the mean of those of Aluminium and Indium, and this places it in a position which had already been assigned to it in the periodic table before its discovery; for, owing to a gap in the system, Mendelejew had asserted its existence five years previously, although he then knew nothing of its characteristic spectral signs, namely, two beautiful violet lines. Radium, too, which was discovered in 1900 and was found to have the atomic weight 226, completely satisfied this test and fitted exactly into the place which this number reserved for it in the table. Thus prediction and confirmatory discovery were fully congruent in this case; the experiment followed on the visionary insight just as a Euclidean proof follows on a mathematical assertion, and we have every reason to say that the system of Mendelejew and Lothar Meyer has stood the crucial test. Future hypotheses will perhaps supplement the system or enlarge our knowledge of it, but will certainly not reduce it ad absurdum.
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Apart from these cases, there are achievements by men who may be called lucky discoverers, although they displayed no genius for finding nor for creating. The philosopher-physicist, Ernst Mach, has devoted a lecture to such intellects, which seems to me very valuable, if only for the reason that he traces back the conceptions of discovery and invention to one common root of knowledge, and explains their difference as being due only to a difference in the application of this discovery.
But when Ernst Mach in this lecture, "On the Influence of Accidental Circumstances on the Development of Inventions and Discoveries," extends the influence of chance to include accidental circumstances that can only enter when the discoverer is closely attentive, it seems to me that certain limitations are advisable. Otherwise, if we pursue Mach's line of thought to its extreme, we could declare every discovery to be due to chance, and this would be the end of the intuitive-creative idea. This assertion would ultimately mean that genius owes its achievements to the accidental arrangement of the molecules in the brain-cells of its associated body. This would be just as wrong as saying that chess is a game of chance because we lose a game when, by chance, we come up against a better player.
Huyghens, the great discoverer and inventor, says, in his Dioptrica, that he would have to consider anyone who invented the telescope without the favourable intervention of chance to be a superhuman genius. Why should he choose just the telescope? To many the invention of the Differential Calculus will appear grander and due to a higher degree of ingenuity. And since it was produced quite methodically, and since chance was excluded, we may follow Huyghens and with good reason proclaim its authors superhuman geniuses.
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Many a true inspiration is dependent on some impulse from without. Who discovered Electromagnetism? The world-echo answers, "Oersted," with the same confidence that it couples together the names America and Columbus. This shows how enormously important was the achievement. Next to steam-power nothing has exerted such a revolutionary influence in all branches as electromagnetism. Without it, the world of to-day would present a totally different aspect. Without it, we should have no dynamos, no electric trams, no telegraphy, no electric-power stations, all of which are due to the work of Arago, Gay-Lussac, Ampère, Faraday, Gramme, and Siemens. Without it, there would be none of the abundance of brilliant discoveries that are associated with the names of Maxwell, Hertz, and Einstein. The fact that physics used to be divided into three parts—Mechanics, Optics, Electrodynamics—and that, since then, the coherent unity of the physical picture of the world has been developed, shows us a picture in the background of which we see the illuminating figure of Hans Christian Oersted. It must not be overlooked, however, that in the case of his great discovery, too, chance played a definite part. It occurred one day when Oersted was holding a lecture in the winter of 1819-20; a magnetic needle situated near his Volta-battery began to vibrate irregularly. This apparently unimportant trembling of the metal points contained the key to a fact, the whole consequences of which could in no conceivable way have entered the mind of this observer of a hundred years ago, in spite of the genius of the Danish scientist, which is documented in the classical and far-famed dissertation, "Experimenta circa effectum conflictus electrici in Acum magneticam," which appeared in July 1820. It cleared the way for intuitions that were equally as fruitful for theory as for practice. Thirteen years after this initial discovery the world saw the first very important consequence in Gauss' and Weber's electric telegraph, and a little later the eminent discoverer Fechner, in Leipzig, proclaimed it as his conviction that, within two years, electromagnetism would entirely reform the world of machines, and would entirely supersede steam- and water-power. Of course, his time estimate fell far short of the mark. It has been reserved for the present generation to realize that we live in an electromagnetic world, and that we have, theoretically and practically, to spend our life electromagnetically. The first indication of this knowledge hung upon the quivering point of a magnetic needle, and from it there evolved the electromagnetic ideas that we are so fond of picturing as our handmaids, but which, in reality, are sovereign over us all.
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A great deal of the history of discovery must be revised and corrected. The Spiral of Archimedes is not due to Archimedes, nor Marriotte's Law to Marriotte, nor Cardan's formula to Cardan, nor Crookes' Tube to Crookes, and Galvanism is only related to Galvani by the following anecdote. It arose from an accidental experience of Madame Galvani in the kitchen: a half-skinned frog that was to be fried for the evening meal happened to rest between a scalpel and a tin plate, which brought it into metallic contact with an accidental discharge of electricity; the frog twitched; the head of the house gave a very naïve interpretation to the phenomenon; and it was under such auspices that Galvanism made its entry into the world. It would be a futile task to endeavour to trace the connexion between experiment and the underlying idea, which, in this case, first came to life in Alexander Volta. What would have remained a mere frog-dance if left to Galvani now acquired the rank of a discovery through the work of a thinking physicist, who set up a "Voltaic series"; this discovery then assumed power and dignity in the hands of Nicholson, Davy, Thomson, Helmholtz, and Nernst. The words Galvanic Electricity should be made to give way entirely to Voltaic Electricity,[4] as in the case of many another expression for which chance and insufficient thought have stood sponsor.
[4]The usual term in England is Voltaic Electricity, or, simply, Current Electricity.—H. L. B.