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applied to purposes of vulgar utility, were not slow in recogniz ing the affront. But Gilbert's quarry was no sect; he blazed hostility at the whole ruck of scholastic hair-splitters. "I renounce all subtleties connected with letters. I depend upon things which may be made evident to the senses, things which may be easily tried," he says; and then again and again he pours out invective upon those who "stuffed the booksellers' shops by copying from one another extravagant stories concerning the attraction of magnets and amber, without giving any reason from experiment," and upon the philosophers "in tenebris somniantes," in a way that makes the later thunder of the Baconian Jove sound like mere echo.
For nineteen years Gilbert had been at work. Never before were the tidings of such great discoveries crowded into so few pages, or told in terser or more vigorous Latin. There is a preface, an address to the author, seemingly by one of his pupils, and then a page devoted to the "interpretation of certain words." I reproduce from this page one line:
Electrica, quæ attrahunt eadem ratione vt electrum.
This is the first mention of the word "electric," and thus the father of the science christened it.
The whole work is divided into six books, and it sets forth nearly every fundamental fact upon which our present knowledge of magnetic phenomena depends. It announces the discovery of the magnetic poles and of the neutral space between them, and the great generalization that like magnetic poles repel, while unlike magnetic poles mutually attract. It draws the distinction between magnets which have poles, and magnetic bodies, such as iron, which have no poles, but which will attract either pole of the magnet. It declares that the earth itself is a huge magnet, which causes the compass needle to assume its north and south position; which magnetizes iron bars placed upright for a considerable time, or hammered while held in the magnetic meridian; or which converts steel bars into magnets when they are cooled standing parallel to the same meridian after being heated red hot. It announces the properties of the armature or
keeper when applied to the poles of a magnet. It describes how iron filings arrange themselves in strange figures in the field of magnetic force, producing the magnetic spectrum, as we now call it. It shows that the magnet-the loadstone-is merely an ore of iron. It says that a magnet when heated loses its magnetic property. It points out how to measure the magnetic force by opposing it to gravity.
All this, however, relates to magnetism. How, it may be asked, do such discoveries bear upon electricity? The question carries with it its own answer, for in its very terms it draws a distinction between magnetism and electricity. Before Gilbert there was no such distinction. He made it. He found all these things true of the magnet, and compared them with the phenomena of amber; and then, like the star which resolved itself into twin worlds before the telescope of Herschel, so, at the bidding of Gilbert, the sister sciences of electricity and magnetism stood asunder.
The second chapter of the second book of "De Magnete contains the famous differentiation between electric and magnetic effects. It opens characteristically with a sharp onslaught upon the groping philosophers, and a scarcely more complimentary reference to the theologians who placed such matters beyond human comprehension. Gilbert then mentions the attractive energy of the amber as hitherto supposed to be confined to that substance and to jet, equally bituminous, and then suddenly, almost dramatically, he begins:
"Nam non solum succinum et gagates (ut illi putant) allectant corpuscula," not only do amber and jet when rubbed attract small bodies, but the same property is in the diamond, the sapphire, the carbuncle, the iris, the amethyst, the opal, the vincentina, the Bristol stone, the beryl, and the crystal. The attractive virtue is likewise in glass, especially when clear and transparent, in all false gems, glass of antimony, most sparry substances and belemnites, in sulphur, mastic sealing-wax, hard resin, sal gem, talc, and rock-alum; and all of these substances will attract not only straws (and just here he cannot resist the temptation of stepping aside to demolish one Alexander Aphrodiseus, who had propounded the remarkable theory that amber would attract the
stalks but not the leaves of the garden basil; why, not stated), but also all metals, wood, stones, water, earth, and, in short, whatever is solid and the object of our senses.
Nam non fo
Tum fuccinum, & gagates (vt illiputant) alle&tant corpufcula; fed Adamas,Sapphirus, Carbunculus, Iris gemma, Opalus, Amethyftus, Vincentina, & Briftolla (Anglica gemma fiue fluor) Berillus, & Cryftallus idem faciunt. Similes etiam attrahendi vires haberc videntur vitrum (præfertim clarum, & lucidum) tum ex vitro, aut Cryftallo adulterata gemmæ, vitrum antimonij, & fluores plurimi ex fodinis, & Belemnites. Allicit etiam fulphur, maftix, & cera du ra figillaris ex lacca varijs coloribus tincta, compofita. Allicit refina durior,vt arfenicum,fed imbecillius; ægrè etiam & obfcurè in conuenienti cœlo ficco Sal gemma, lapis fpecularis,& alumen rupeum. Quod videre licet, cum aer media Hyeme rigidas fuerit, & clarus, tenuifque cum effluuia telluris electrica minus impediunt, & electrica firmius indurefcunt; de quibus poftea. Alliciunt hæc omnia non feftucas modò & paleas; fed metalla omnia, ligna, folia, lapides, terras, aquam ipfam, &oleum; omnraque quæ fenfibus noftris fubijciuntur, aur folida funt: quanquàm fcribant non attrahere fuc cinum nifi paleas, &ramenta quædam, (quarè falfò Alexander Aphrodifeus inexplicabilem quæftionem dicit effe de fuccino, quòd tantum ficcas attrahar paleas, nec folia ocimi) fed illæ falfiffima, & turpiffimæ funt fcriptorum narrationes. Scd vtpoteris manifestà experiri quomodò talis fit attractio, & quæ fintille materiæ, quæ a◄ lia fic alliciunt corpora, (ad quarum nonnullas etiamfi corpora in clinant, tamen propter imbecillitatem non attolli ab illis videntur, fed facilius conuertuntur) fac tibi verforium ex quouis metallo, longitudinis trium vel quatuor digitorum, fatis leue fuprà acum fuam, more indicis magnetici, cuius alteri fini appone fuccinum,vel
lapillum leniter fricatum,nitidum & politum, nam illico verforium
I reproduce this remarkable passage, famous now for all time, and most profoundly characteristic of its writer; for, not content
with making these startling announcements, he tells the reader in the very next sentence to prove them for himself, and then produces the first of all electrical instruments, the balanced needle electroscope. Here is his picture of it. It is a thin strip of metal balanced like a compass needle, which, when an electrified body, such as rubber, amber, or glass, is presented to one of its ends, will turn on its axis, thus showing the fact of the electrification.
All these substances which act like amber Gilbert called electrics, and his differentiation of electrics and the magnet is masterly in its direct simplicity and power of contrast. The magnet, he says, will attract only magnetic bodies; all things are drawn to the electric. Magnets will carry great weights. A magnet weighing but a couple of ounces will sustain a load of half an ounce or even an ounce. Electrics will support only the lightest weights. A piece of amber weighing three ounces will barely support the load of a quarter of a grain of barley. The magnet will attract magnetic bodies anywhere and through anything, in air or in water, through metals or wood or stone. But damp air" suffocates the virtue " of electrics, and there will be no motion of the attracted body if paper or cloth be interposed. Here is a strong suggestion of insulation, not discovered until a century and a quarter later. He observed that an electrical body placed near a flame lost its charge, that resinous or unctuous bodies will attract most vigorously, that electrical appearances are strongest in dry weather, that the most effectual friction is that which is light and quick; and he held that electrical attraction is a general property of matter, contrasting strongly with magnetic attraction, which he regarded as peculiar only to magnets and magnetic bodies.
"Nothing in this treatise has been done in haste," says Gilbert; "every experiment has been carefully repeated." Small wonder that he gave nineteen years to it, for the book is a monument of inductive reasoning erected upon a mountain of heaped-up experiments. The scientific world received it with the highest commendation. Barrow ranked Gilbert with Gassendus, Mersennes, and Descartes. Sir Kenelm Digby compares him to Harvey, the discoverer of the circulation of the
blood. Galileo thought him "worthy of the greatest praise," and procuring a loadstone made in globular form (Gilbert's terrella, or little earth), repeated his experiments.
However great the interest may be which attaches to the opinions of other men concerning Gilbert's discoveries, it can never rival that with which the student of history will seek to learn those of Francis Bacon. But he will close the pages of the "De Augmentis" and the "Novum Organon " with a feeling that the great philosopher has been anew revealed in one of those side lights which bring out characteristics of him that the world would rather forget. It may be possible to believe that, in his treatment of Gilbert, Bacon was influenced by "an honest ambition;" but no one, without violating his own intelligence, will be disposed to accredit him with the "enlarged philanthropy " or "sincere love of truth" with which Macaulay thinks he became imbued while in his library, even if he gave little evidence of its possession elsewhere. It is hard to perceive strict veracity in the writer of the nineteenth aphorism of the "Novum Organon," who, with a complete knowledge of Gilbert's recorded work of years before, can say that the way of discovering truth which "derives axioms from the senses and particulars, rising by a gradual and unbroken ascent so that it arrives at the most general axioms last of all, is the true way, but as yet untried." What name shall be given to the peculiar form of misrepresentation which, being unable to avoid the truth, smirches it after this fashion?
"It generally happens that men make their trials carelessly, and, as it were, in play, slightly varying experiments already known, and if the thing does not answer, growing weary and abandoning the attempt. And even if they apply themselves to experiments more seriously and earnestly, and labor seriously, still they spend their labor in working out some one experiment, as Gilbert with the magnet, and the chemists with gold; a course of proceeding not less unskillful in design than small in attempt."
Where is the foundation for such expressions of contempt as electricity (of which Gilbert and others after him have devised such stories) is nothing else than the appetite of a body when excited by gentle friction"? But mark the "after him," which almost compensates for the sneer at the "stories." Or what