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engagement, is in a great measure proportioned to the figure that the injured perfon makes; the vows and proteftations of lovers are an illustrious example of this obfervation, for these commonly are little regarded when made to women of inferior rank.
CHA P. V.
MOTION AND FORCE.
HAT motion is agreeable to the eye without relation to purpose or defign, may appear from the amusement it gives to infants: juvenile exercises are relished chiefly up
on that account.
If a body in motion be agreeable, one will be apt to conclude, that at rest it must be disagreeable: but we learn from experience, that this would be a rafh conclufion. Reft is one of those circumstances that are neither agreeable nor difagreeable, being viewed with perfect indifferency. And happy it is for mankind that the matter is fo ordered: if reft were agreeable, it would difincline us to motion, by which all things are performed: if it were disagreeable, it would be a fource of perpetual uneafinefs; for the bulk of the things we fee, appear to be at reft. A fimilar inftance of defigning wisdom I have had occafion to explain, in oppofing grandeur to littleness, and elevation to lowness of place *. Even in the simplest matters, the finger of God is confpicuous: the happy adjustment
• See chap. 4.
of the internal nature of man to his external circumftances, difplay'd in the inftances here given, is indeed admirable..
Motion is certainly agreeable in all its varieties of quicknefs and flowness; but motion long continued admits fome exceptions. That degree or continued motion which correfponds to the natural courfe of our perceptions, is the moft agreeable *. The quickelt motion is for an inftant delightful: but it foon appears to be too rapid: it becomes painful, by forcibly accelerating the course of our perceptions. Slow continued motion becomes difagreeable for an oppofite reafon, that it retards the natural course of our perceptions t.
There are other varieties in motion, befide quickness and flowness, that make it more or less agreeable regular motion is preferred before what is irregular; witnefs the motion of the planets in orbits nearly circular: the motion of the comets in orbits lefs regular, is lefs agreeable.
Motion uniformly accelerated, refembling an afcending feries of numbers, is more agreeable than when uniformly retarded: motion upward is agreeable by the elevation of the moving body. What then fhall we fay of downward motion regularly accelerated by the force of gravity, com
*See chap. 9.
+ This will be explained more fully afterward, ch. 9.
pared with upward motion regularly retarded by the fame force? Which of these is the most agreeable? This question is not easily folved.
Motion in a straight line is agreeable but we prefer undulating motion, as of waves, of a flame, of a fhip under fail: fuch motion is more free, and alfo more natural. Hence the beauty of a ferpentine river.
The eafy and fliding motion of fluids, from the lubricity of their parts, is agreeable upon that account: but the agreeablenefs chiefly depends upon the following circumftance, that the motion is perceived, not as of one body, but as of an endless number moving together with order and regularity. Poets ftruck with this beauty, draw more images from fluids in motion than from folids.
Force is of two kinds; one quiefcent, and one exerted in motion. The former, dead weight for example, must be laid afide; for a body at reft is not by that circumftance either agreeable or difagreeable. Moving force only belongs to the present fubject; and though it is not feparable from motion, yet by the power of abftraction, either of them may be confidered independent of the other. Both of them are agreeable, because both of them include activity. It is agreeable to fee a thing move to fee it moved, as when it is dragged or pufhed along, is neither agreeable nor difagreeable, more than when at reft. It is agreeable to fee a thing exert force; but it makes
not the thing either agreeable or difagreeable, to fee force exerted upon it.
Though motion and force are each of them agreeable, the impreffions they make are different. This difference, clearly felt, is not easily defcribed. All we can fay is, that the emotion raised by a moving body, refembling its caufe, is felt as if the mind were carried along the emotion raifed by force exerted, refembling alfo its caufe, is felt as if force were exerted within the mind.
To illuftrate this difference, I give the following examples. It has been explained why smoke afcending in a calm day, suppose from a cottage in a wood, is an agreeable object *; fo remarkably agreeable, that landscape-painters introduce it upon all occafions. The afcent being natural, and without effort, is delightful in a calm ftate of mind it refembles a gently-flowing river, but is more agreeable, because ascent is more to our taste than defcent. A fire-work or a jet d'eau roufes the mind more; because the beauty of force visibly exerted, is fuperadded to that of upward motion. To a man reclining indolently upon a bank of flowers, afcending fmoke in a ftill morning is delightful; but a fire-work or a jet d'eau roufes him from this fupine posture, and puts him in motion.
A jet d'eau makes an impreffion distinguishable from that of a water-fall. Downward motion