Heroes of Science: Physicists. Garnett William

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СКАЧАТЬ prism, the other by a prism held in the hand, and superposing the latter on the former so that different colours were made to coincide. This experiment was repeated in a modified form, nearly two hundred years later, by Helmholtz, who found that the mixture of blue and yellow lights produced pink. Unfortunately, Boyle's spectra were far from pure, for, the source of light being of considerable dimensions, the different colours overlapped one another, as in Newton's experiments, and in consequence some of his conclusions were inaccurate. Thus blue paper in the yellow part of the spectrum appeared to Boyle green instead of black, but this was due to the admixture of green light with the yellow. He concluded that bodies appear black because they damp the light so as to reflect very little to the eye, but that the surfaces of white bodies consist of innumerable little facets which reflect the light in all directions. In the same year he published some "Observations on a Diamond, which shines in the Dark;" and an extensive treatise on "Some Considerations touching the Style of the Holy Scriptures." Next year appeared several papers from his pen, the most important being "Occasional Reflections upon Several Subjects," the wide scope of which may be gathered from the title. His "New Experiments and Observations touching Cold" were printed in 1665. In this paper he discussed the cause of the force exerted by water in freezing, methods of measuring degrees of cold, the action of freezing-mixtures, and many other questions. He contended that cold was probably only privative, and not a positive existence.

      Lord Bacon had asserted that the "essential self" of heat was probably motion and nothing more, and had adduced several experiments and observations in support of this opinion. In his paper on the mechanical origin of heat and cold, Boyle maintained that heat was motion, but motion of the very small particles of bodies, very intense, and taking place in all directions; and that heat could be produced by any means whatever by which the particles of bodies could be agitated. On one occasion he caused two pieces of brass, one convex and the other concave, to be pressed against each other by a spring, and then rubbed together in a vacuum by a rotary motion communicated by a shaft which passed air-tight through the hole in the cover of the receiver, a little emery being inserted between them. In the second experiment the brasses became so hot that he "could not endure to hold [his] hand on either of them." This experiment was intended, like the rubbing of the blocks of ice in vacuo by Davy, to meet the objection that the heat developed by friction was due to the action of the air. The following extract from a paper intended to show that the sense of touch cannot be relied upon for the estimation of temperature, shows that Boyle possessed a very clear insight into the question:—"The account upon which we judge a body to be cold seems to be that we feel its particles less vehemently agitated than those of our fingers or other parts of the organ of touching; and, consequently, if the temper of that organ be changed, the object will appear more or less cold to us, though itself continue of one and the same temperature." To determine the expansion of water in freezing, he filled the bulb and part of the stem of a "bulb tube," or, as it was then generally called, "a philosophical egg," with water, and applying a freezing-mixture, at first to the bottom of the bulb, he succeeded in freezing the water without injury to the glass, and found that 82 volumes of water expanded to 91-1/8 volumes of ice—an expansion of about 11-1/8 per cent. Probably air-bubbles caused the ice to appear to have a greater volume than it really possessed, the true expansion being about nine per cent. of the volume of the water at 4°C. The expansion of water in freezing he employed in order to compress air to a greater extent than he had been able otherwise to compress it. Having nearly filled a tube with water, but left a little air above, and then having sealed the top of the tube, he froze the water from the bottom upwards, so that in expanding it compressed the air to one-tenth of its former volume.

      Magnetism and electricity came in for some share of Boyle's attention. He carried out a number of experiments on magnetic induction, and found that lodestones, as well as pieces of iron, when heated and allowed to cool, became magnetized by the induction of the earth. His later experiments with exhausted receivers were not made with his first pump, but with a two-barrelled pump, in which the pistons were connected by a cord passing over a large fixed pulley, so that, when the receiver was nearly exhausted, the pressure of the air on the descending piston during the greater part of the stroke nearly balanced that on the ascending piston. In this respect the pump differed only from Hawksbee's in having the pulley and cord instead of the pinion and two racks. It also resembled Hawksbee's pump in having self-closing valves in the pistons and at the bottom of the cylinders, which, in this pump, had their open ends at the top. The pistons were alternately raised and lowered by the feet of the operator, which were placed in stirrups, of which one was fixed on each piston. The lower portions of the barrels were filled with water, through which the air bubbled, and this, occupying the clearance, enabled a much higher degree of exhaustion to be produced than could be obtained without its employment.

      In 1665 Boyle was nominated Provost of Eton, but declined to accept the appointment. His "Hydrostatical Paradoxes," published about this time, contain all the ordinary theorems respecting the pressure of fluids under the action of gravity demonstrated experimentally.

      In 1677 Boyle printed, at his own expense, five hundred copies of the four Gospels and the Acts of the Apostles in the Malayan tongue. This was but one of his many contributions towards similar objects.

      On November 30, 1680, the Royal Society chose Boyle for President. He, however, declined to accept the appointment, because he had conscientious objections to taking the oath required of the President by the charter of the Society.

      It appears that very many of Boyle's manuscripts, which were written in bound books, were taken away, and others mutilated by "corrosive liquors." In May, 1688, he made this known to his friends, but, though these losses put him on his guard, he complained afterwards that all his care and circumspection had not prevented the loss of "six centuries of matters of fact in one parcel," besides many other smaller papers. His works, however, which have been published are so numerous that it would take several pages for the bare enumeration of their titles, many of them being devoted to medical subjects. The edition published in London in 1743 comprises nearly three thousand pages of folio. Boyle always suffered from weak eyes, and in consequence he declined to revise his proofs. In the advertisement to the original edition of his works the publisher mentioned this, and at the same time pleaded his own business engagements as an excuse for not revising the proofs himself! It was partly on account of the injury to his manuscripts, and partly through failing health, that in 1689 he set apart two days in the week, during which he declined to receive visitors, that he might devote himself to his work, and especially to the reparation of the injured writings. About this time he succeeded in procuring the repeal of an Act passed in the fifth year of Henry IV. to the effect "that none from thenceforth should use to multiply gold or silver, or use the craft of multiplication; and if any the same do, they should incur the pain of felony." By this repeal it was made legal to extract gold and silver from ores, or from their mixtures with other metals, in this country provided that the gold and silver so procured should be put to no other use than "the increase of moneys." It is curious that Boyle seems always to have believed in the possibility of transmuting other metals into gold.

      His sister, Lady Ranelagh, died on December 23, 1691, and Boyle survived her but a few days, for he died on December 30, and his body was interred near his sister's grave in the chancel of St. Martin's-in-the-Fields. Dr. Shaw, in his preface to Boyle's works, writes, "The men of wit and learning have, in all ages, busied themselves in explaining nature by words; but it is Mr. Boyle alone who has wholly laid himself out in showing philosophy in action. The single point he perpetually keeps in view is to render his reader, not a talkative or a speculative, but an actual and practical philosopher. Himself sets the example; he made all the experiments he possibly could upon natural bodies, and communicated them with all desirable candour and fidelity." The second part of his treatise on "The Christian Virtuoso," Boyle concluded with a number of aphorisms, of which the following well represent his views respecting science:—

      "I think it becomes Christian philosophers rather to try whether they can investigate the final causes of things than, without trial, to take it for granted that they are undiscoverable."

      "The book of Nature is a fine and large piece of tapestry СКАЧАТЬ