century, came, as time went on, to be | embrace the influences of Providence, and to more and more fully personated by her be diligent in the inquiry of everything we handmaiden, "natural history," until at meet with. For we shall quickly find that the last the identity of the one was completely number of considerable observations and inmerged in that of the other. The interventions this way collected, will a hundredfold outstrip those that are found by design. No mediary whom they had admitted as a man but hath some lucky hits and useful messenger of higher promise, they were thoughts on this or that subject he is concompelled to take for better for worse. versant about, the regarding and communiLike Malvolio, they had wooed the mis- cating of which might be a means to other tress; like Sir Toby, they wedded the persons highly to improve them. . . . This maid. way is also more grateful to both the writer and the reader, who proceed with a fresh stomach upon variety, but would be weary and dull'd if necessitated to dwell too long upon one subject.* We shall conclude our remarks on this singular essay by transcribing some specimens of the queries directed by Hooke to future investigators. Even after the lapse of above two centuries, they strike us as suggestive and ingenious. Under the heading of ether, he asks: Whether it permeates all bodies, be the medium of light, be the fluid body in which the air is but as a tincture? Whether it cause gravity, in the earth or other celestial bodies? Of the atmosphere: — Whether it encompasseth the sun and planets, and that each of them have a peculiar atmosphere, as well as they have a gravitating power? Whether the spots in the sun may not be clouds of smoke or vapors, raised up into that atmosphere? Whether meteors have anything of fire in them, or whether the light may not be an effect of their rapid motion? * of his career. Although Hooke's "True Method' was not published until after his death, we may safely attribute it to an early stage He was a man whose ideas did not change, but were superseded. They retained their original form, but were crowded out of sight by the multitude of new arrivals. Now we have evidence to show that, without wholly abandoning his early faith in the efficacy of his "Philosophical Algebra," his confidence in an approaching renovation of science was replaced, later in life, by a conviction of its infinite complexity and extent. In the preface to a volume of lectures, published in 1674, he says: For as there is scarce one subject of millions that may be pitched upon, but to write an exact and complete history thereof would require the whole time and attention of a man's life, and some thousands of inventions and observations to accomplish it: so on the other side no man is able to say that he will complete this or that inquiry, whatever it be, (the greatest part of invention being but a lucky hit of chance for the most part not in our own power). 'Twill be much better, therefore, to Posthumous Works, p. 29. Thus we see that discovery, which speculation had proclaimed to be the infallible result of system, was by experi ence declared to be the lucky outcome of chance. Investigators had previously been commanded to march in a compact army along the highway of method towards the metropolis of knowledge; they were now warned to disperse in all possible directions into the wilderness of phenomena, and beat the bushes of nature for what game they might contain. That one view was equally misleading with the other is obvious; that one should form the reaction from the other was inevitable. Hooke's reasons for discursiveness were not so much the guide of his conduct as its apology. His position as curator of experiments to a body inordinately greedy of scientific novelty suggested a wide range of subjects for enquiry, which his native versatility induced him to embrace to its fullest extent. The journals and registers of the Royal Society alone convey, by their records, an adequate idea of his prodigious activity of mind, fertility of resource, and experimental skill. Astronomy, optics, acoustics, thermotics, pneumatics, hydrostatics, magnetism, and chemistry; geology, phys iology, meteorology, and psychology, all in turn engaged his attention, and all in turn received illustrations from his sagacity, and impulses from his zeal. all men who ever lived, he was perhaps the most prolific in mechanical invention. New instruments, or useful modifications of those already in use, flowed from him by the dozen. An arithmetical machine, a triple writing-machine, a deep-sea sounding machine, a wind-gauge, rain-gauge, hygrometer and odometer, a system of telescopic telegraphy, a "water-poise," a "weather-clock," and a species of micro Of * An Attempt to prove the Motion of the Earth. London, 1674. phone, were all due to his ingenuity; | dred years, however, had to elapse before besides important improvements in as- they could be profitably employed. In tronomical and other instruments -tele- his "Method for making a History of the scopes, quadrants, micrometers, diving- Weather," the attention of observers is bells, barometers, thermometers, and especially directed to the following "parbalances. He speculated curiously on ticulars," as "requisite for the raising of memory, and calculated the number of axioms whereby the cause or laws of ideas of which the human mind is suscep- weather may be found out." I. The tible, estimating it at three thousand one strength and quarter of the winds. 2. hundred and fifty-five million, seven hun- The degrees of heat and cold. 3. The dred and sixty thousand! He constructed degrees of dryness and moisture observed a model for the rebuilding of London after with a hygroscope "made with the sinthe great fire, which was approved, al- gle beard of a wild oat perfectly ripe, set though not adopted; and was the archi- upright and headed with an index." 4. tect of Hoxton Hospital and other build- The degrees of pressure of the air. 5. ings. He read before the Royal Society | The constitution and face of the sky. commentaries on Ovid's "Metamor- It is perhaps worth remarking that our phoses," Plato's "Atlantis," and Hanno's present system of meteorological observaPeriplus," interpolating these critical tions corresponds with tolerable accuracy excursions between geological theories to Bacon's notion of how a "history" of and astronomical observations. To him any special branch of physics should be was due the ingenious idea of measuring compiled; with this difference in result, the force of gravity at different altitudes that, instead of arriving at "axioms" and by the rate of vibration of a pendulum of "forms," we have as yet obtained only a a given length; as well as the determina- set of empirical rules which, however tion (so far as the actual state of chemical practically useful, can scarcely be said to knowledge permitted it to be determined) constitute a science. of the true function of the air in combus Discoursed with Mr. Hooke [Pepys wrote, tion and respiration. His zeal carried August 8, 1666] about the nature of sounds, him to the length of making, in an ex- and he did make me understand the nature of hausted receiver, his own person the sub-musicall sounds made by strings, mighty pretject of his observations "the only tily; and told me that having come to a certain experiment of that kind," his biographer naïvely remarks, "I think ever tried." number of vibrations proper to make any tone, Sa At the present time, when weather prophecies have come to form a recognized part of our complex social machinery, it would be ungrateful to omit noticing that Hooke was the first to propose a scientific system of meteorological forecasting. Notwithstanding Mr. Pepys's sceptiHis scheme, as might be expected, had cism, Hooke was on this occasion not for its basis the close association (re-"refining' "overmuch. He exhibited in marked by him among the earliest) of 1681 an instrument (with the principle of changes of weather with barometrical which he had doubtless long been acvariations; "which," he writes to Boyle, quainted) for counting the pulsations of October 6, 1664, sound, which seems to have been virtually identical with that now known as 66 vart's wheel." He also anticipated Chlad ni's celebrated experiment by strewing flour on a vibrating glass bell, thus presenting to the eye, as it were, a picture of the configuration of rest and motion on its surface. It was one of his favorite ideas that, by some future discovery, the sense of hearing would be reinforced as prodigiously as the sense of sight had already gularly realized by the recent invention of been by the telescope an intuition sinthe telephone. "It has not yet been if it continue to do as I have hitherto observed it, I hope it will help us one step towards the raising a theorical pillar or pyramid, from the top of which, when raised and ascended, we may be able to see the mutations of the weather at some distance, before they approach us; and thereby being able to predict and forewarn, many dangers may be prevented, and the good of mankind very much promoted.* The means recommended by him for the furtherance of this noteworthy object were the same in principle as those now in use at all the meteorological observatories of Europe and America. Two hun * Boyle's Works, vol. vi., p. 492. Published by Sprat, History of the Royal Society, p. 173. f' Pepys's Diary, vol. iv., p. 43. Bright's ed. 66 thoroughly examined," he wrote in 1664,* | 1679 helped to soothe the vanity of the 99.66 We now come to the relations of Hooke with Newton. The first collision between these two remarkable men occurred on the subject of their respective optical discoveries. Hooke's merits in this direction were very considerable. He was the first to propound that view as to the nature of light now universally accepted under the name of the "undulatory theory." He held that light is a "very short, vibrative motion," originating in an agitation of the minute particles of the luminous body, and propagated through a perfectly homogeneous and elastic medium by direct or straight lines, extended every way, like rays from the centre of a sphere, just after the same manner (though indefinitely swifter) as the waves or rings on the surface of the water do swell into bigger and bigger circles about a point of it, where by the sinking of a stone the motion was begun."* Of Hooke's private and personal history there is little to be recorded. His life might almost be comprised in two words - experiments and controversies. In 1664, Sir John Cutler instituted, espe- Further, he hit upon the principle of cially for his benefit, a mechanical lecture- "interference," which, neglected by Huyship of 50l. a year; in the following year ghens and ignored by Newton, was deshe was appointed to the professorship of tined, in the hands of Young and Fresnel, geometry founded by Sir Thomas Gres- to afford demonstrative proof of the truth ham in 1575His services as curator of the hypothesis roughly sketched by were remunerated by an annual stipend Hooke. In his "Micrographia" (justly of 30%., not perhaps very regularly paid, styled by Pepys "a most excellent piece ") since we hear, on one occasion, that both he described, besides a series of beautihe and Halley were offered, in lieu of ful observations with the microscope, the their respective salaries, an equivalent phenomenon known in optical treatises number of copies of that unlucky "His- as the "colors of thin plates," and with tory of Fishes," by the publication of singular sagacity declared it to form the which the Royal Society had drained their experimentum crucis as regards chromatic finances and cumbered their shelves. The light. These "fantastical" tints (which famous controversy between Hooke and we may recognize every summer's day in Hevelius on the subject of plain or tele- the iridescent glancing of some insect's scopic sights, which agitated the learned wing) Hooke diligently examined in soapworld of Europe during many years, has bubbles, in "muscovy-glass" (mica), in long ago sunk into a silence we need not metallic films, and other similar subdisturb. Hevelius was in the wrong and stances. His explanation of what he obobstinate; Hooke was in the right, but served contains a remarkable, although offensive. Astronomers in general seemed necessarily imperfect, approximation to a disposed to prefer some slight uncertainty cardinal truth in optics. By a double as to the position of the stars to being reflection from two closely adjacent surbullied into precision by the magisterial faces, he tells us,† the rays of light are little hunchback of Gresham College. broken up into "confused or duplicated The dispute remained long in the condi- pulses," changing in tint with the varying tion of a smouldering flame, with out- thickness of the reflecting film. Thus, breaks of argument at distant intervals,"colors begin to appear, when the pulses and Halley's mission of conciliation in of light are blended so well and so near together that the sense takes them for one." According to the modern doctrine of "interference," waves of light, Micrographia, pp. 56-7. + Ibid. p. 66. Posthumous Works, p. 190. & R. pursuing each other at the distance of Newton acknowledged that if he saw farhalf an undulation, mutually destroy each ther than most men, it was "by standing other, and produce darkness. But, be- on the shoulders of giants." Hooke cause difference of color means difference thought his own mental stature sufficient of wave-length, a doubly-reflecting surface, to entitle him to reject such extraneous by destroying or reinforcing, according to aids. He accordingly set aside without its varying thickness, undulations of cer- hesitation Newton's discovery, offering his tain lengths, analyzes white light into the criticisms, not indeed discourteously, but prismatic rays of which it is composed, with a certain air of superiority which not and thus produces the appearances char- a little galled his sensitive antagonist. acteristic of "thin plates." Matters were aggravated three years later when Newton published his beautiful explanation, on the emission hypothesis, of the colors of thin plates. Hooke declared "that the main of it was contained in the Micrographia,' a remark extremely offensive to Newton, who, however, with his usual careful justice, immediately extended his somewhat scanty acknowledgment of his rival's labors, by defining with scrupulous accuracy the measure in which he was indebted to him. That Hooke was not devoid of generous sentiments appears from a letter which he wrote about this time to Newton, proposing a private correspondence on philosophical subjects.* In it he acknowledges the superior abilities of the great mathematician, professes a dislike to contention, and hints that their relations had been embittered by the machinations of ill-disposed persons. (Oldenburg is evidently indicated.) Newton's reply was conceived in a corresponding spirit; but the harmony thus established was unhappily not lasting. The flaw in Hooke's theory was his erroneous idea as to the nature of color. And on this point we are unable to defend him from the charge of culpable ignorance. The true view was proposed to him, and he deliberately rejected it. The keystone of the arch he had attempted to build was offered to him, and he declined to set it in its place. On February 8, 1672, Newton's memorable paper on the composition of white light was read before the Royal Society. Had Hooke frankly accepted the discovery, and applied it as a bulwark to his own tottering hypothesis, his name would doubtless have sounded louder in the ears of posterity. But here his moral failings, as well as his intellectual shortcomings, interposed. He was, primarily, an experimentalist. His delight was rather in the things than in the thoughts of nature. The intimate relations of objects were of less account in his eyes than their external operation on the senses. Add to this the utilitarian tendency impressed upon physical researches by the Baconian precepts. In the preface to the "Micrographia" Hooke described as follows the purposes of the Royal Society: "They do not wholly reject experiments of mere light and theory, but they principally aim at such, whose application will improve and facilitate the present way of manual arts." And similar declarations were made by Boyle and other leading men of the time. Thus, in Hooke's apprehension, the raison d'être of an hypothesis was not so much to suggest a physical connection of facts as to provide a convenient classification of experiments, and its most essential quality that it should be plausible, not that it should be true. His judgment was besides warped, even more than that of most men, by that intellectual egotism which, if it sometimes acts as a spur to progress, more often performs the office of a drag. His selflove blinded him to the real merits of his competitors. His own speculations loomed so large before him as to exclude from his field of view those of every other. The problem of gravity was the supreme question of that time. It stood first among the orders of the day of the scientific council. It was instinctively felt that until it should be disposed of, no real progress could be made in physical knowledge. And, slowly but surely, the way was being prepared for a great discovery. Galileo had made Newton possible. Men's ideas were gradually clarifying; the great cosmical analogies, now so familiar, were step by step emerging out of the dusk of ignorance; antiquated prepossessions were sinking, in a sediment of cloudy cavil, out of sight. Heaven was assimilated to earth, and earth to heaven; the old gratuitous separation between the starry firmament over our heads and the solid globe under our feet was abolished by acclamation; and it was felt that the coming law, to be valid, must embrace in its operation the whole of the visible universe. Towards this consummation Gilbert contributed some * Brewster, Life of Newton, vol. i., p. 138. But this I durst promise the undertaker, that he will find all the great motions of the world to be influenced by this principle, and that the true understanding thereof will be the true perfection of astronomy.* thing by his theory of universal magnet- | be, will mightily assist the astronomer to reism; and Galileo, as well as Bacon and duce all the celestial motions to a certain rule, Horrocks, foresaw that in this direction which I doubt will never be done without it. lay the coveted secret. In 1645 the Abbé Boulliau (Bullialdus) actually announced that the force by which the sun holds the planets in their orbits must vary as the inverse square of their distance from him; in 1666 Borelli published at FlorOur readers will perceive that he was ence some suggestive speculations on the at this time still at fault as to the rate of subject; † in England, Wallis, Wren, and decrease of the central force; but, some Halley, all eagerly scanned the ques- years later, this too was divined by him tion, and all arrived at close approxima- divined, not demonstrated. In 1679 he tions to the truth. But it was undoubt-wrote to Newton, suggesting the law of edly Hooke whose arrow flew nearest inverse squares, or "reciprocal duplicate to the mark. The first definite proposal proportion," and it was this letter which of the planetary revolutions as a problem led the Cambridge philosopher to "rein mechanics is due to him; and it has been immemorially held that prudens quæstio est dimidium scientiæ. In a paper on gravity, presented by him to the Royal Society, March 21, 1666, the following noteworthy passage occurs: If such a principle (central attraction) be supposed, all the phenomena of the planets seem possible to be explained by the common principle of mechanic motions; and possibly the prosecuting this speculation may give us a true hypothesis of their motion, and from some few observations, their motions may be so far brought to a certainty, that we may be able to calculate them to the greatest exactness and certainty that can be desired.‡ On this matter, at least, Hooke's ideas were persistent and progressive. In 1674 he announced a forthcoming "system of the world, answering in all things to the common rules of mechanical motions, and founded on the three following supposi tions: but also all the First, that all celestial bodies whatsoever have an attraction or gravitating power towards their own centres, whereby they attract not only their own parts other celestial bodies that are within the sphere of their activity. Second, that all bodies whatsoever that are put into a direct and simple motion, will so continue to move forward in a straight line till they are, by some other effectual powers, deflected and sent into a motion describing a circle, ellipsis, or some other more compounded curve line. Third, that these attractive powers are so much the more powerful in operating by how much the nearer the body wrought upon is to their own centres. Now, what these several degrees are, I have not yet experimentally verified, but it is a notion which, if fully prosecuted, as it ought to sume his former thoughts concerning the moon."+ He first, as is well known, attempted the problem of assimilating the force of gravity at the earth's surface to the deflecting power exerted on the moon's orbital motion, in 1665, when he "gathered "the duplicate proportion from Kepler's third law; but the defective data then at his command obliged him to suspend his speculations. Now, with the results of Picard's improved degree measurement in his hands, he once more set his gigantic powers to their equally gigantic task. Having made some progress with the calculations, he, however, again "threw them by, being upon other studies;" and it required a further fillip to induce him to complete them. It was given thus. One January day in 1684, Edmund Halley, a young and rising astronomer, having independently worked out the great problem so far as to perceive the necessity for the ratio of inverse squares, came to town from Islington, and, falling into discourse with Wren and Hooke on the subject, the latter "affirmed that upon that principle all the laws of the celestial motions were to be demonstrated, and I declared," that he himself had done it. continues Halley,§ "the ill success of my attempts, and Sir Christopher, to encourage the enquiry, said that he would give Mr. Hooke some two months' time to bring him a convincing demonstration thereof, and besides the honor, he of us that did it should have of him a present of a book of forty shillings. Mr. Hooke then said he had it, but should conceal it |