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leagues off, perceptible to the inhabitants about


-Odours, likewise, though these seem always attended with a corporeal emission of the odoriferous substance, operate at considerable distances, as appears to such as sail along the coasts of Florida, or some parts of Spain, where there care whole groves or woods of lemons, oranges, and the like odoriferous trees; or thickets of rosemary, marjoram, &c.+ And lastly, sounds, but particularly the rays of light, operate to prodigious distances‡.

But all these virtues, whether they operate to small or large distances, certainly operate to finite ones, and such as are known to nature, so that there are certain fixed bounds which they cannot exceed, and that in proportion either, 1. to the bulk and quantity of the bodies; or, 2. to the strength or weakness of the virtues; or, 3. to the suitableness or unsuitableness of the medium, all which ought to be carefully observed, and brought to computation §. And again, the measures of those called violent motions, or

**See Mr. Boyle's History of Cold.

See Mr. Boyle of Effluvia.

See Mr. Boyle, Dr. Hook, Sir Isaac Newton, the Philosophical Transactions, French Memoirs, &c.

Here we may observe the proper use of calculation, or mathematics, in physics.

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the motions of projectiles, as bullets from guns, the motions of carriages, &c. ought to be observed and determined, for these also have manifestly their fixed limits.

There are, likewise, certain motions and virtues, contrary to those that operate by contact, and not at a distance, as acting at a distance, and not by contact; and again, others that operate weaker at a small distance, and stronger at a greater.

Thus vision is not well performed in contact, but requires a certain medium, and a certain distance, to be perfect; though I have been assured, by a person of veracity, who was couched for cataracts in his eyes, (which is an operation performed by means of a small silver needle, thrust between the first coat of the eye, to remove and force away the film of the cataract into the corner of the eye) that he clearly saw the needle moving over the pupilla, or sight of the eye*.

But allowing this, it is manifest that larger objects cannot be well or distinctly seen, except in the vertex of a cone, made by the converging of the rays from some distance. Thus old men see better when the object is removed a little farther off, than when it is near. And it is certain, that

* See Sir Isaac Newton's Optics, particularly the queries at the end thereof.

in projectiles, the percussion is not so strong at too small a distance, as it is soon after, or at the due distance. The measures, therefore, of these things, and others of the like kind, are to be set down, to determine their motion in point of distance.

We must not omit another kind of local measure of motions, which regards not progressive, but spherical motion; that is, the expansion of bodies into a larger sphere, or their contraction into a less. For we should enquire, among the measures of motion, what degree of compression or extension bodies, according to their nature, may easily and readily suffer, and at what point they begin to resist, and at length will sustain no more. Thus when a blown bladder is compressed, the air sustains some degree of compressure, but if the compressure be too great, the air enduring it no longer, bursts the bladder, and frees itself.

But to make a more exact experiment to this purpose, we took a small, light, and thin metalline bell, and plunged it into a bason of water, so that it carried down along with it the air contained in its cavity, to the bottom of the vessel, where we had first placed a little ball, which the cavity of the bell was to fall upon. When this ball was little in proportion to the cavity of the bell, the air shrunk itself into a less compass, without

escaping; but if the ball was so large, that the air could not freely yield, the air would then, as being impatient of a greater pressure, raise up the bell, on one side, and ascend in bubbles*.

Again, to try what degree of extension air is capable of, we took a glass egg, with a small orifice at one end thereof, and by strong suction drew out the air, then immediately stopping the orifice with the finger, we plunged the glass in water, where the finger being removed, the air that was stretched and dilated by the suction, now endeavouring to contract itself, (so that if the glass had not been plunged in water, it would have drawn in the external air with a hissing noise) it drew in such a quantity of water as sufficed to recover the remaining air to its former bulk or dimension +.

And it is certain, that pneumatical, or rare bodies, such as the air, will suffer a remarkable contraction; but that tangible bodies, such as water, suffer compression with much greater difficulty, and in a less degree. What this degree might be, we attempted to discover by the following experiment.

*The design was here, to estimate the force wherewith air resists its own condensation, or endeavour to escape. See Mr. Boyle's Pneumatical Experiments, particularly Abridgm. Vol. II. p. 670–672.

+ See Mr. Boyle's Works, Abridgm. Vol. II.



We caused a hollow and strong globe of lead to be formed, capable of containing two wine pints, and having made a hole therein, we filled the globe with water, then soldered up the orifice with lead, and now beat the sides of the globe flat out with a large hammer; whence the water was of necessity contracted, because a sphere is the figure of largest capacity. And when hammering was of no farther service in making the water shrink, we put the lead vessel into a press, and squeezed it, till at length the water forced itself through the solid lead, and stood upon its surface like a dew. We afterwards computed into how much less space the water was driven by this violent pressure*.

But solid, dry, or more compact bodies, as stones, wood, and metals, sustain a much less, and almost imperceptible compression and extension, and either release themselves by breaking, moving, squeezing out, or other evasions, as appears in the bending of wood or metal, in spring clocks or watches, in projectiles, hammering, and numerous other motions.


But all these particulars, together with their measures, are to be discovered and set down, in

* See the Experiments of the Academie del Cimento; and Mr. Boyle's Works, Abridgm, Vol. I. p. 628, 629, Vol. II. p. 290, 666, 703, &c.

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