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Philosophical Trausactions of that year, I find it stated that two mathematicians, a Mr. Munckley, of Lincoln's Inn; and a Mr, Bevis, saw a comet on the 30th of April in that year; and on two or three evenings afterwards, near the horizou in the south; one of the accounts is not quite clear as to whether it bad a tail or not; it states, that it appeared to him to be rather surrounded with a circular haziness than a tail. The other saw a tail on the 1st of May, but not afterwards ; though La Place says, that the same comet in the year 1456 had a long tail, which spread consternation over all Europe! The commencement of Mr. Bevis's letter is rather curious; he says, 'I had acquainted some of my friends, that it was my opinion a comet would hardly rise above our horizon of London, Sunday, April the 29tb; but that probably we might see one on April 30th. Wonderful to tell, be says he accordingly did see one on Monday! Who, or what, could have put him in possession of the secret? The first time both these gentlemen saw it, was on the same eveving; and the comet having answered the important purpose of fulfilling the predictions of Halley, Clairault, and Bevis, it quickly retired, without, I believe, ever having once been seen by the people of either England or France."
We arrive next at the chapter on the supposed diurnal motion of the earth. Mr. Prescot ludicrously states, that this belief is founded only on the experiments of a spindle and soft ball of clay, iron hoop, mop, pendulum, and measurements of a degree of the earth!
The theory which is here attacked, maintains that the earth is of an oblate form, which necessarily results from the centrifugal motion, and by way of EXPERIMENT, (says Mr. Prescot) they
“Stick a spindle through the centre of a soft ball of clay, and by spinning it briskly, they observe that the clay has a tendency to contract at the poles, and fly off the spindle! A certain astronomical professor exhibits the same effects by a thin iron hoop and a rod. • That this,' says he, must be the consequence, appears from this experiment; that if you take a thin iron hoop and make it revolve swiftly about one of its diameters, that diameter will be diminished, and the diameter which is perpendicular to it will be increased; now if we suppose the earth to revolve, the parts most distant from its axis must, from their greater velocity, have a greater tendency to fly off from the axis, and, therefore, that diameter which is perpendicular to the axis, must be increased.' Another admired author says, the same doctrine is proved by a mop! When a mop,' says he, 'is turned upon the arm by a quick circular motion, the threads or thrums are observed to rise highest in the middle, and the swifter the mop is whirled, the greater will be the force, and the particles will fly off with the greater velocity.'"
" The earth has no iron axis stuck through its poles, nor any other kind of axis from which its parts can recede, and therefore your experiment is quite inapplicable. But even were it otherwise, the manifest effect of a centrifugal force, operating with an impulse according to
the experiment, and the theory founded upon it by Newton, would be instant destruction to the globe : because if, by a revolution in twenty-four hours, or in any other given time, that force could so far exceed the power of gravity, as to protuberate seventeen miles on the equator, I cannot conceive any thing to prevent it from rapidly increasing ; for, according to theory, the gravity of the equatorial parts would decrease as those parts swelled out: and the diurnal motion continuing the same, the motion of the eqnatorial parts would increase by a uniform acceleration, until the whole would separate, and fly away from the centre. I remember, when I was at a pottery, that in the process of forming a vessel upon the wheel; suppose globular, or egg-shaped ; if the rapid motion of the spindle over balanced the cohesive temper of the clay, and thereby forced the forming vessel to swell out beyond its prescribed gauge, a cootinuance of the same velocity of motion would continue to increase its diameter, until it suddenly burst, and flew off the wheel in pieces. As therefore the globe is not so affected in the least, it is sufficiently manifest that the theory is false."
Another experimental proof was derived from the unequal vibrations of the pendulum, which it was asserted beat slower at the equator than nearer to the poles.
“ Messrs. Picart and De la Hire, however, instead of ascribing the alterations in the vibration to the force of more, or less, gravity, produced experiments to prove, that the observed effects might possibly be caused by an increase of heat, in the torrid zone, lengthening the rods, and consequently lengthening the vibrations; or by cold producing the contrary effects.
66 When I formerly wrote upon this subject, I expressed an opinion, that the increased density of the air, on approaching towards the poles, would more naturally account for the irregularity of the pen dulum's motion, than the fancied distortion of the globe. Since then, on looking into the Philosophical Transactions, I find something like a confirmation of that opinion in the account there recorded of Dr. Derham's experiments. In treating of the figure of the earth, he seems to have paid no regard to the pretended experiments of the pendulum under the equator; ' For,' says he, I have shewn' (No. 294, Phil. Trans.) “from the like variations in the air-pump, that this may arise from the rarity of the air there more than here. And in No. 480, the same writer is more particular; relating some experiments he had made on pendulums vibrating in an exhausted receiver, he observed, that the arches of vibration, in vacuo, were larger than in the open air, or in the receiver before it was exhausted : that the enlargement or diminution of the arches of vibration, were constantly proportional to the quantity of air, or rarity or density of it, which was left in the receiver of the air-pump. And as the vibrations were larger shorter, so the times were accordingly : viz two seconds in an hour when the vibrations were largest, and less and less as the air was re-admitted, and the vibrations shortened.' • Hence, VOL. I. PART II.
says Mr. Stone, “the resistance of the air must certainly be a considerable obstacle to the equable going of a clock.'”
Kepler and Cassini were of opinion, that the eartb was of an oval or egg form. To this was opposed the centrifugal forces of the Newtonian theory. Louis XIV. in honor of his subjects, ordered the whole arc of the meridian passing through France to be measured, and afterwards sent philosophers to the northern and southern parts of the earth. The difference appears to be one inch in twenty feet. Our author is very sceptical in the result.
" How far so small a difference (says he) could be certainly ascertained under the pitiable circumstances in which these poor frost-bitten mathematicians were placed, let the reader candidly judge from the account given by the French; whether the Swedés were more comfortably circumstanced I am not informed.
"In measuring the base line," says Maupertius, “we separated into two bands, each of which carried four rods of fir, each thirty feet long. I shall say nothing of the fatigues and dangers of this operation.
Judge what it must be, to walk in snow two feet deep, with heavy poles in our hands, which we were obliged to be continually laying on the snow and lifting again: in a cold so excessive, that whenever we could taste a little brandy, (the only thing that could be kept liquid,) our tongues and lips froze to the cup and came away bloody; in a cold that congealed the fingers of some us, and threatened us with still more dismal accidents; while the extremities of our bodies were thus freezing, the rest, through excessive toil, was bathed in sweat.”
“The philosophers who travelled to the south, had, if possible, still greater difficulties to encounter. When placed upon the high mountains, making their observations, besides experiencing excessive cold, they were sometimes in such danger of being blown down the precipices, that even their Indian attendants were frightened away from them. In these dreary and alarming situations, both companies had to measure their base lines ;-their terrestrial and celestial angles : -afterwards to try to reduce their measures to the level of the sea ! And with all these extraordinary difficulties to surmount, they gravely professed to have discovered, that a degree under the equator, or at the polar circle, measured a quarter of a mile, more or less, than one in France! With as much colour of reason they might have asserted, that in the midst of a storm, they could shoot an arrow, so skilfully as to split a hair at the distance of fifty yards! For even if they had had none of the difficulties to encounter which I have mentioned, an error of one-fourth of a minute in their celestial observations, would have rendered all their other operations useless ; because such error would have comprehended as great a quantity as the assigned differ
And every man, who is experienced in the use of instruments for taking angles, will, if he be candid, acknowledge the impossibility
of measuring them to a certainty within much less than a minute particularly in the inconvenient situations I lave described-even leaving out other weighty considerations, such as the imperfections of eye-sight, instruments, and the continual variations in the state of aërial refractions. The swagging oftheir measuring poles 'would cause a considerable error; and even the póle itself, if measured by a metallic foot, would be shorter in the northern than it would be in the southern latitudes. So that upon a just consileration of all the unconquerable obstacles that every where opposed these philosophers, through the whole process of their undertaking, I am of opinion, that Mr. La Lande, (in his History of Astronomy for 1805,) might have spared his expression of surprise, that his countrymen should have committed such a mistake at Tornea : the thing most surprising, in my opinion, is, that the measures of the different parties“ should so nearly coincide with each other, unless it be supposed, that théory required a tolerably near agreement!"
The next chapter is devoted to a disquisition on the motion of the earth in an orbit, which our author considers to be imaginary and contradicted, by sight, reason, and Scripture ! He says, the Newtonians
" Are so well satisfied of the utter insufficiency of all their elaborate arguments and boasted experiments to produce a direct and manifest proof, or any proof at all, to invalidate the divine assertion, that they are constrained to declare, that were it not for the 'fixed stars, it would be extremely difficult, if not impossible, to prove the motion of the earth. We should suppose that the planets made a complete revoJution between any two similar situations with respect to the sun, because the places of elongation are similarly described, and are in quantity the same, whether the earth be in motion or not. It is from the apparent motion of the sun with respect to the fixed stars, that we conclude that the earth describes an orbit in about three hundred and sixty-five days.' Posterity will, I believe, read with astonishment, that the men of this age, by looking at the sun in motion, supposed it to stand still! And there is no appearance, even according to their own admission, and consequently no proof, of the earth's motion; why not draw the natural and obvious conclusion, that the sun really describes the orbit which he appears to do? That, however, would not 'suit their purpose, and therefore they go on to assert, that the strongest objection that can be made against the earth's motion round the sun, is that, in opposite points of the earth's orbit, its axis, 'which always keeps a parallel direction, would point to different fixed,stars, which is not found to be the fact. But this objection is easily removed by considering' (not' by experiment,) the immense distance of the fixed stars, in respect of the diameter of the earth's orbit, the latter being no more than a point when compared with the 'former.' Thus they consider a thing as they would have it, and then they positively assert that it is so !”.
“Further, he says, we are required to believe, that in December, we are about 200,000,000 of miles from the place we left in June, though we cannot possibly discover, by the most exact observation of the polar star, that we bave moved one inch !"
" The result of all observations made to ascertain this point has been, that the declinations of the fixed stars are every day in the year the same to a hair's breadth.”
The author next discusses the theories of the atmosphere and the void spaces for planetary motion, which he maintains are refuted by decisive facts.
“Philosophers almost unvaryingly confound the elasticity or spring of the air, with its weight, and accordingly conclude, that a base of an inch square supports a column of air of fifteen pounds' weight; and by the same rule a middle-sized man is constantly pressed by about fifteen tops of air! Now, if that be true, how is it that a man exists, when, by mounting aloft in a balloon, until the barometer falls to ten or twelve inches, the pressure upon him, according to that rule, is suddenly reduced two-thirds, or about ten tons ? When Mr. Robertson ascended at Hamburgh, a few years ago, it does not appear that he bursted, or even experienced any inconvenience whatever, from that cause, although the quicksilver in his barometer suuk as low as twelve inches and a balf. Mr. Baldwin, too, when he ascended from Chester, in the year 1785, expressly mentions, that he experienced no inconvenience whatever; nor did Mr. Brydone when on the summit of Etna; the French on the Andes; or Dr. Heberden on the peak of Teneriffe. Others, I admit, are said to have experienced some difficulty of breathing when placed in elevated situations; but what does that prove? Not an increase of rarity, but the reverse. Dr. Fletcher, formerly an English envoy at the court of Russia, states, that when you there pass out of a warm room into a cold one, you will “sensibly feel your breath to wax stark and even stifling with the cold as you draw it in and out.” The same sensation is mentioned by the French philosophers as felt by them at Tornea; in breathing they said their breasts seemed to be rent. The experieuce of every one proves that breathing is more difficult in frosty weather, when the density of the air is increased by cold, than in warm weather when it is rarefied by heat.”
The state of the ocean, Mr. Prescot thinks an irresistible proof against the theories of the atmosphere, gravity, and earthly motion. Speaking of his opponents, he says,
“ After having laboured hard, for about one hundred and forty years, to balance and compact the elementary parts of the system, they have been so astonishingly remiss, as to leave the ocean to the uncontrolled operation of three mighty forces, which would, in the first hour of the earth's motion, have completely swept it out of its bed, had not the Creator wisely ordered the matter otherwise."
66 Those who have witnessed the effects of a storm of wiod upon the ocean, which wind, even in a hurricane, is not supposed to move with a velocity greater than one huodred and forty miles in an hour, may ca sily conceive what would be the consequence to the ocean if the