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to be heavy, and its motion must not be too rapid, otherwise the resistance of the air will destroy too much of the motion; but in the kitchen-jack, as well as in the striking part of a clock, where the superfluous force is purposely destroyed, the fly is made light, and strikes the air with a broad surface. An effect similar to that of a fly and a spring is sometimes produced in hydraulic machines by the introduction of an air-vessel, the air contained in which is compressed more or less according to the intensity of the force, and exerts a more uniform pressure in expelling the fluid which is forced irregularly into it. See Young's Lectures.

WHEEL, in the military art, is the word of command, when a battalion or squadron is to alter its front either one way or the other. To wheel to the right, directs the man in the right angle to turn very slowly, and every one to wheel from the left to the right, regarding him as their centre; and vice versa when they are to wheel to the left. When a division of men are on the march, if the word be to wheel to the right or to the left, then the right or left hand man keeps his ground, only turning on his heel, and the rest of the rank move about quick till they make an even line with the said right or left hand man.

WHEELS, water. See MILL.

WHIRLWIND, a wind that rises suddenly, is exceedingly rapid and impetuous, in a whirling direction, and often progressively also; but it is commonly soon spent. Dr. Franklin, in his Physical and Meteorological Observations, read to the Royal Society in 1756, supposes a whirlwind and a water-spout to proceed from the same cause: their only difference being, that the latter passes over the water, and the former over the land. This opinion is corroborated by the observations of many others, who have remarked the appearances and effects of both to be the same. They have both a progressive as well as a circular motion; they usually rise after calms and great heats, and mostly happen in the warmer latitudes the wind blows every way from a large surrounding space, both to the water-spout, and whirlwind; and a water-spout has, by its progressive motion, passed from the sea to the land, and produced all the phenomena and effects of a whirlwind; so that there is no reason to doubt that they are meteors arising from the same general cause, and explicable upon the same principles, furnish

ed by electrical experiments and discoveries.

WHISPERING places, are places where a whisper, or other small noise, may be heard from one part to another, to a great distance. They depend on a principle, that the voice, &c. being applied to one end of an arch, easily passes by repeated reflections to the other.

Hence sound is conveyed from one side of a whispering gallery to the opposite one, without being perceived by those who stand in the middle. The form of a whispering gallery is that of a segment of a sphere, or the like arched figure; and the progress of the sound through it may be illustrated in the following manner: Let A B C (Plate XVI Miscel. fig. 12.) represent the segment of a sphere; and I suppose a low voice uttered at A, the vibrations extending themselves every way, some of them will impinge upon the points, E, E, &c.; and thence be reflected to the points, F, F, &c.; thence to G, G, &c.; till at last they meet in C; where, by their union, they cause a much stronger sound than in any part of the segment whatever, even at A, the point from whence they came. Accordingly, all the contrivance in whispering places is, that near the person who whispers there may be a smooth wall, arched either cylindrically or elliptically. A circular arch will do, but not so well.

The most considerable whisperingplaces in England are, the whisperinggallery in the dome of St. Paul's, London, where the ticking of a watch may be heard from side to side, and a very easy whisper be sent all round the dome. The famous whispering-place in Gloucester cathedral is no other than a gallery above the east end of the choir, leading from one side thereof to the other. It consists of five angles and six sides, the middlemost of which is a naked window, yet two whisperers hear each other at the distance of twenty-five yards.

WHISTON, (WILLIAM,) an English divine, philosopher, and mathematician, of uncommon parts, learning, and extraordinary character, was born the 9th of December, 1667, at Norton, in the county of Leicester, where his father was rector. He was educated under his father till he was seventeen years of age, when he was sent to Tamworth school, and two years after admitted of Clare-hall, Cambridge, where he pursued his studies, and particularly the mathematics, with great diligence.

In 1693, he was made Master of Arts, and Fellow of the College, and soon after commenced one of the tutors; but his ill state of health soon after obliged him to relinquish this profession. Having entered into orders, in 1694, he became chaplain to Dr. More, Bishop of Norwich; and while in this station he published his first work, entitled A New Theory of the Earth, &c." in which he undertook to prove that the Mosaic doctrine of the earth was perfectly agreeable to reason and philosophy; which work, having much ingenuity, brought considerable reputation to the author

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In the year 1698, Bishop More gave him the living of Lowestoff in Suffolk, where he immediately went to reside, and devoted himself with great diligence to the discharge of that trust. In the beginning of the last century he was made Sir Isaac Newton's deputy, and afterwards his successor in the Lucasian professorship of mathematics, when he resigned his living at Lowestoff, and went to reside at Cambridge. From this time his publications became very frequent, both in theology and mathematics. By his researches into the writings of the Fathers, he was led to embrace the Arian hypothesis respecting the person of Christ; on account of which he was, in October, 1710, deprived of his professorship, and expelled the University of Cambridge, after he had been formally convened and interrogated for some day's together. At the conclusion of this year he wrote his "Historical Preface," after wards prefixed to his "Primitive Christianity Revived," containing the reasons for his dissent from the commonly received notions of the Trinity, which work he published the next year in four vols. 8vo. for which the Convocation fell upon him most vehemently.

In 1713, he and Mr. Ditton composed their scheme for finding the longitude, which they published the year following, a method which consisted in measuring distances by means of the velocity of sound.

On Mr. Whiston's expulsion from Cambridge, he went to London, where he conferred with Doctors Clarke, Hoadly, and other learned men, who endeavoured to moderate his zeal, but he was not to be intimidated; he continued to write, and to propagate his opinions with as much ardour as if he had been in the most flourishing circumstances; which, however, were so bad, that in 1721, a

subscription was made for the support of his family, which amounted to 4701. For though he drew some profits from reading astronomical and philosophical lectures, and also from his publications, which were very numerous, yet these of themselves were very insufficient: nor, when joined with the benevolence and charity of those who loved and esteemed him for his learning, integrity, and piety, did they prevent his being frequently in great distress.

In 1739, Mr. Whiston put in his claim to the mathematical professorship at Cambridge, then vacant by the death of Dr. Saunderson, in a letter to Dr. Ashton, the Master of Jesus College; but no regard was paid to it. Among a variety of works, he published Memoirs of his own Life and Writings, which are very curi

ous.

Whiston continued many years a mem ber of the established church; but at length forsook it on account of the reading of the Athanasian Creed, and went over to the Baptists; which happened while he was at the house of Samuel Barker, Esq. at Lindon, in Rutlandshire, who had married his daughter; where he died after a week's illness, the 22d of August, 1752, at upwards of eighty-four years of

age.

The character of this conscientious and worthy man has been attempted by two very able personages, who were well acquainted with him, namely, Bishop Hare, and Mr. Collins, who unite in giving him the highest applauses for his integrity, piety, &c. Mr. Whiston left some children bebind them; among them, Mr. John Whiston, who was for many years a very considerable bookseller in London.

WHITE, one of the colours of bodies. Though white cannot properly be said to be one colour, but rather a composition of all the colours together; for Newton has demonstrated that bodies only appear white by reflecting all the kinds of colouralike; and that even the light the sun is only white, because it consists of all colours mixed together.

ed rays

This may be shown mechanically in the following manner: Take seven parcels of coloured fine powders, the same as the primary colours of the rainbow, taking such quantities of these as shall be proportional to the respective breadths of these colours in the rainbow, which are of red 45 parts, orange 27, yellow 48, green 60, blue 60, indigo 40, and of violet 80; then mix intimately together these seven

parcels of powders, and the mixture will be a whitish colour : and this is only similar to the uniting the prismatic colours together again, to form a white ray or pencil of light of the whole of them. The same thing is done conveniently thus: Let the flat upper surface of a top be divided into 360 equal parts, all around its edge; then divide the same surface into seven sectors, in the proportion of the numbers above, by seven radii or lines drawn from the centre; next let the respective colours be painted in a lively manner on these spaces, but so as the edge of each colour may be made nearly like the colour next adjoining, that the separation may not be well distinguished by the eye; then, if the top be made to spin, the colours will thus seem to be mixed all together, and the whole surface will appear of a uniform whiteness: and if a large round black spot be painted in the middle, so as there may be only a broad flat ring of colours around it, the experiment will succeed

the better.

White bodies are found to take heat slower than black ones; because the latter absorb or imbibe rays of all kinds and colours, and the former reflect them. Hence it is that black paper is sooner inflamed by a burning glass, than white; and hence also, black clothes, hung up in the sun by the dyers, dry sooner than white ones.

WHITEHURST, (JOHN,) in biography, an ingenious English philosopher, was born at Congleton, in the county of Cheshire, the 10th of April, 1713, being the son of a clock and watch-maker there. On his quitting school, where it seems the education he received was very defective, he was bred by his father to his own profession, in which he soon gave hopes of his future eminence.

At about the age of twenty-one, his eagerness after new ideas carried him to Dublin, having heard of an ingenious piece of mechanism in that city, being a clock with certain curious appendages, which he was very desirous of seeing, and no less so of conversing with the maker. On his arrival, however, he could neither procure a sight of the former, nor draw the least hint from the latter concerning it. Thus disappointed, he fell upon an expedient for accomplishing his design; and accordingly took up his residence in the house of the mechanic, paying the more liberally for his board, as he had hopes from thence of more readily obtaining the indulgence wished for. He

was accommodated with a room directly over that in which the favourite piece was kept carefully locked up; and he had not long to wait for his gratification: for the artist, while one day employed in examining his machine, was suddenly called down stairs; which the young inquirer happening to overhear, softly slipped into the room, inspected the machine, and presently satisfying himself as to the secret, escaped undiscovered to his own apartment. His end thus compassed, he shortly after bid the artist farwell, and returned to his father in England.

About two or three years after his return from Ireland, he left Congleton, and entered into business for himself at Derby, where he soon got into great employment and distinguished himself very much by several ingenious pieces of mechanism, both in his own regular line of business, and in various other respects, as in the construction of curious thermometers, barometers, and other philosophical instruments, as well as ingenious contrivances for water-works, and the erection of various larger machines, being consulted in almost all the undertakings in Derbyshire, and in the neighbouring counties, where the aid of superior skill in mechanics, pneumatics, and hydraulics was requisite.

In this manner his time was fully and usefully employed in the country, till, in 1775, when the act being passed for the better regulation of the gold coin, he was appointed stamper of the money-weights; an office conferred upon him, altogether unexpectedly, and without solicitation. Upon this occasion, he removed to London, where he spent the remainder of his days, in the constant habits of cultivating some useful parts of philosophy and mechanism.

In 1778, Mr. Whitehurst published his Inquiry into the Original State and Formation of the Earth; of which a second edition appeared in 1786, considerably enlarged and improved; and a third in 1792. This was the labour of many years; and the numerous investigations necessary to its completion were in themselves also of so untoward a nature, as, at times, though he was naturally of a strong constitution, not a little to prejudice his health. When he first entered upon this species of research, it was not altogether with a view to investigate the formation of the earth, but in part to obtain such a competent knowledge of subterraneous geography, as might become

subservient to the purposes of human life, by leading mankind to the discovery of many valuable substances which lie conceated in the lower regions of the earth.

May the 13th, 1779, he was elected and admitted a Fellow of the Royal Society. Before he was admitted a member, three several papers of his had been inserted in the Philosophical Transactions, viz. Thermometrical Observations at Derby, in vol. 57: An account of a Machine for raising Water, at Oulton, in Cheshire, in vol 65; and Experiments on Ignited Substances, vol. 66: which three papers were printed afterwards in the collection of his works in 1792.

In 1783, he made a second visit to Ireland, with a view to examine the Giant's Causeway, and other northern parts of that island, which he found to be chiefly composed of volcanic matter: an account and representation of which are inserted in the latter editions of his Inquiry. Dur. ing this excursion he erected an engine for raising water from a well to the summit of a hill, in a bleaching ground at Tullidoi, in the county of Tyrone, which is worked by a current of water.

In 1787, he published An Attempt toward obtaining Invariable Measures of Length, Capacity, and Weight, from the Mensuration of Time. His plan is, to obtain a measure of the greatest length that conveniency will permit, from two pendulums whose vibrations are in the ratio of 2 to 1, and whose lengths coincide nearly with the English standard in whole numbers. The numbers which he has chosen show much ingenuity. On a supposition that the length of a second's pendulum, in the latitude of London, is 391 inches, the length of one vibrating 42 times in a minute must be 80 inches; and of another vibrating 84 times in a minute, must be 20 inches; and their difference 60 inches, or five feet, is his standard mea

sure.

By the experiments, however, the difference between the lengths of the two pendulum rods, was found to be only 59,892

inches instead of 60, owing to the error in the assumed length of the second's pendulum, 391 inches being greater than the truth, which ought to be 394 very nearly. By this experiment, Mr. Whitehurst obtained a fact, as accurately as may be in a thing of this nature, viz. the difference between the lengths of two pendulum rods whose vibrations are known: a datum from whence may be obtained, by calculation, the true lengths of pendulums,

the spaces through which heavy bodies fall in a given time, and many other particulars relating to the doctrine of gravitation, the figure of the earth, &c.

Mr. Whitehurst had been at times subject to slight attacks of the gout, and he had for several years felt himself gradually declining. By an attack of that disease in his stomach, after a struggle of two or three months, it put an end to his laborious and useful life, on the 18th of February, 1788, in the 75th year of his age, at his house in Bolt Court, Fleetstreet, being the same house where another eminent self-taught philosopher, Mr. James Ferguson, had immediately before him lived and died.

WILKINS, (Dr. JOHN,) in biography, a very ingenious and learned English bishop and mathematician, was the son of a goldsmith at Oxford, and born in 1614. After being educated in Greek and Latin, in which he made a very quick_progress, he was entered a student of New Inn in that University, when he was but thirteen years of age; but after a short stay there, he was removed to Magdalen Hall, where he took his degrees. Having entered into holy orders, he first became chaplain to William Lord Say, and afterwards to Charles Count Palatine of the Rhine, with whom he continued for some time. Adhering to the Parliament during the civil wars, they made him warden of Wadham College about the year 1648. In 1656, he married the sister of Oliver Cromwell, then lord protector of England, who granted him a dispensation to hold his wardenship, notwithstanding his marriage. In 1659, he was by Richard Cromwell made master of Trinity College in Cambridge; but ejected the year following, upon the restoration. He was then chosen preacher to the Society of Gray's Inn, and rector of St. Lawrence Jewry, London, upon the promotion of Dr. Seth Ward to the bish. oprick of Exeter. About this time he became a member of the Royal Society, was

chosen of their council, and proved one

of their most eminent members. He was afterwards made dean of Rippon, and in 1668 bishop of Chester; but died of the stone in 1672, at fifty eight years of age.

Burnet writes, that "he was a man of as great a mind, as true a judgment, as eminent virtues, and of as good a soul, as any he ever knew; that though he married Cromwell's sister, yet he made no other use of that alliance, but to do good offices, and to cover the university of

Oxford from the sourness of Owen and Goodwin. At Cambridge, he joined with those who studied to propagate better thoughts to take men off from being in parties, or from narrow notions, from superstitious conceits, and fierceness about opinions. He was also a great observer and promoter of experimental philosophy, which was then a new thing, and much looked after. He was naturally ambitious, but was the wisest clergyman I ever knew. He was a lover of mankind, and had a delight in doing good."

Of his publications, which are all of them very ingenious and learned, and many of them particularly curious and entertaining, the first was in 1638, when he was only twenty-four years of age, viz. "The Discovery of a New World; or, a Discourse, to prove that it is probable there may be another Habitable World in the Moon; with a discourse concern. ing the possibility of a Passage thither." In 1640, " A Discourse concerning a New Planet, tending to prove that it is pro-bable our Earth is one of the Planets " In 1641, "Mercury, or the secret and swift Messenger; showing how a man may with privacy and speed communicate his thoughts to a friend at any distance;" 8vo. In 1648, "Mathematical Magic; or, the Wonders that may be performed by Mathematical Geometry," 8vo. All these pieces were published entire in one volume, 8vo. in 1708, under the title of "The Mathematical and Philosophical Works of the Right Rev. John Wilkins," &c. To this collection is also subjoined an abstract of a larger work, printed in 1668, folio, entitled "An Essay towards a real Character and a philosophical Language."

WILL. In the Hartleyan acceptation of the term, the will is that state of mind which is immediately previous to, and causes those express acts of memory, imagination, reasoning, or bodily motion, which we term voluntary; corresponding to the common acceptation of the term volition. In the more customary use of the term, it comprehends the whole class of feelings by which volition is produced, (for an account of which, see MENTAL PHILOSOPHY, § 63—99.)

It would be an interesting and very important inquiry, how far volition may become connected with and regulate the trains of thought and feeling, and the state of mind which we call attention; but this would lead us into a field which neither our limits of time, nor of space, would allow us to survey even cursorily.

That such connection can be formed in various instances, there is no room for doubt; and were it otherwise, man would be merely the creature of external circumstances that, on the other hand, there are limits to such establishment, is also indisputable; and were it not so, man might become the creator of his own mind, and all the benefits arising from the intellectual and social powers depend upon caprice. But we must content ourselves with laying before our readers some of Hartley's valuable practical remarks respecting the will.

"The will appears to be nothing but a desire or aversion, sufficiently strong to produce an action that is not automatic, primarily or secondarily (§ 101.) The will is therefore that desire or aversion which is strongest for the present time; for if any other desire were stronger, the muscular motion connected with it by association would take place, and not that which proceeds from the will, or the voluntary one.

"Since the things which we pursue do, when obtained, generally afford pleasure, and those which we fly from affect us with pain, if they overtake us, it follows, that the gratification of the will is generally associated with pleasure, the disappointment of it with pain. Hence a mere associated pleasure is transferred upon the gratification of the will; a mere associated pain, upon the disappointment of it: and if the will were always gratified, this mere associated pleasure would, according to the present frame of our natures, absorb, as it were, all our other pleasures; and thus, by drying up the source from whence it sprung, be itself dried up at last; and the first disappointments, after a long course of gratification, would be intolerable. Both which circumstances are sufficiently observable, in an inferior degree, in children that are much indulged, and in adults, after a long series of successful events. Gratifications of the will without the consequent expected pleasure, and disappointments of it without the consequent expected pain, are particularly useful to us here and it is by this, amongst other means, that the human will is brought to a conformity with the divine; which is the only radical cure for all our evils and disappointments, and the only earnest and medium for obtaining lasting happi

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