that I do not in the least exaggerate.* These are truly their own sagacious experiments; their sublime simili

* Dr. Desaguliers laid the following account before the Royal Society, and it was actually received and registered amongst their transactions!

Upon an axis of iron, that could be made to turn swiftly, (by means of a wheel whose string went round a pulley fixed to the said axis,) Dr. Desaguliers slipped on two iron hoops, whose planes intersected each other at right angles, representing two colures, which being in a spring temper, sprung in such a manner as to be one ninety-sixth part longer in that diameter that coincided with the axis, than in the equatorial diameter; this proportion being the same that Mr. Cassini supposes to be between the axis and equatorial diameter of the earth: two circular plates, to which the said hoops were rivetted, had square holes, through which the axis passed; so that the two poles of the oblong spheroid, which the hoops described in their revolution, might approach together in such a manner, as to let them put on the form of a true sphere; when, by the whirling, the equatorial diameter of the machine swelled, and overpowered the elasticity of the hoops: a greater degree of swiftness turned the sphere into an oblate spheroid of Sir Isaac Newton's figure; a velocity still greater makes the disproportion of the diameters, such as those of Jupiter; and still the equatorial diameter increases with the centrifugal force."

Here was an axis of iron; a wheel; a string; a pulley; and two iron hoops; all set in rapid motion, to illustrate, or prove, Newton's imaginary figure of the earth, and by consequence, its rotatory motion! Had he twirled his hoop, before this Royal Society, to prove, that motion would raise the hoop in the middle, his machinery would have answered the object. But, as applicable to the globe, a tee-totum or peg-top would have been more suitable for the purpose; because such being firm and compact, they would have borne a greater similarity to the globe; and, on examination of them, after they had been spun, that learned society would have found, that the operation had not swelled out their sides in the least! No doubt the hoop, by motion, would have flown off in a tangent, had it not been linked to the spindle;-no experiment was necessary to satisfy the learned society of that. The question they should have propounded, according to their own doctrines, ought to have been simply this: can a body revolving in a vacuum, about its own mathematical axis, fly away from itself? Such a question might, at least, have put a stop to the expense of money and time, laid out in pursuing inapplicable experiments. The Newtonian philosophy had then recently triumphed over the Cartesian; and this experiment was brought

tudes! These are some of the facts alluded to by the reverend poet already quoted, upon which rest,

"Those laws that to their mighty orbits chain

The circling spheres, and bound the raging main." We show you, they exultingly exclaim, a system founded on the pyramidal base of experiments! Well, gentlemen, I have not whirled the mop, but I have considered your experiment: yet, I have not been able to discover the least similarity between this beautifully variegated globe, composed of water, soft earth, sand and solid rocks; and your soft ball of clay, iron hoop, and your thrums. But there is another particular in which the globe differs considerably from your experimental instruments, and which seems to have escaped your notice whilst brooding over your favourite experiments; 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

forward to aid in the removal of Cassini's oblong form, in order that Newton's oblate form might occupy its place. The object was to destroy French bubbles, and raise English ones in their room. And this war of bubbles lasted, as I said before, fifty years, produced much froth, and the French Sçavans were conquered!

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the same, the motion of the equatorial parts would increase by a uniform acceleration, until the whole would separate, and fly away from the centre. 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 overbalanced the cohesive temper of the clay, and thereby forced the forming vessel to swell out beyond its prescribed gauge, a continuance 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, and far more calculated to excite the scorn and derision of sensible men, than to form a foundation to support "Newton's immortality of renown!"

Now with regard to the experimental and sensible proofs of the oblate form of the earth, which these philosophers tell their followers they have obtained on the surface of it; I shall first notice that which they pretend to have derived from the unequal vibrations of the pendulum. By observation, they say, it has been found to beat slower at the equator than nearer to the poles; and in order to make a clock keep the same time at the equator as at the city of Paris, it is necessary to shorten the pendulum by a two-hundreth part of the whole length. When this effect was first said to have been observed on pendulums, Sir Isaac Newton and Mr. Huygens laid hold of the incident, and laboured hard to pass it off as a confirmation of their favourite theory of the earth's motion. But mark how widely these philosophical enthusiasts differed in their conclusions, though both calculated from exactly the same data. The former professed to demonstrate mathematically, that the polar

diameter was to the equatorial diameter as 689 to 692, being a difference of the two hundred and thirty-fifth part of the whole diameter; while the latter pretended, likewise, to prove mathematically, that the exact proportion one bore to the other, was as 577 to 875, being a difference of no less than about one-third of the whole diameter ! The fallacy of the latter is sufficiently manifest from the circular appearance of the earth's shadow in a lunar eclipse. But Newton, more wary, well knew, that no observation, made upon the face of the globe, could by any means sensibly prove his statement of the matter to be true; he therefore, (and that was the most material point,) stated the difference to be so exceedingly small, that he had no fears of being detected: and his superior credit as a mathematician, secured to him the faith of his admirers, who, without hesitation, adopted his account of the matter as an important truth not to be questioned.

There were, however, certain learned men, who, in opposition to the demonstrations of these mathematicians, thought the difference in question was caused by the pendulum being affected by circumstances quite unconnected with the form of the earth. Messrs. Picart and De la Hire, two celebrated French philosophers, 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.

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 pendulum's motion,

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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 airpump. And as the vibrations were larger or 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," says Mr. Stone, "the resistance of the air must certainly be a considerable obstacle to the equable going of a clock."

Here then are the opinions and experiments of Picart, De la Hire, Derham and Stone; opposed to the fancies of Sir Isaac Newton and Mr. Huygens, who also, as I have stated, widely differed in their own mathematical conclusions!

Diogenes, an ancient philosopher of Apollonia, successor to Anaxagoras, is said to have held an opinion that the earth was of an oval, or egg form; such also was the notion adopted by Kepler and after him by