Action is a sort of language which perhaps one time or other, may come to be taught by a kind of grammar-rules; but, at present, is only got by rote and imitation: and contrary to most other copyings or imitations, people of rank and fortune generally excel their originals, the dancing-masters, in easy behaviour and unaffected grace; as a sense of superiority makes them act without constraint; especially when their persons are well turn'd. If so, what can be more conducive to that freedom and necessary courage which make acquired grace seem easy and natural, than the being able to demonstrate _when_ we are actually just and proper in the least movement we perform; whereas, for want of such certainty in the mind, if one of the most finish'd gentlemen at court was to appear as an actor on the public stage, he would find himself at a loss how to move properly, and be stiff, narrow, and aukward, in representing even his own character: the uncertainty of being right would naturally give him some of that restraint which the uneducated common people generally have when they appear before their betters. It is known that bodies in motion always describe some line or other in the air, as the whirling round of a fire-brand apparently makes a circle, the water-fall part of a curve, the arrow and bullet, by the swiftness of their motions, nearly a straight line; waving lines are formed by the pleasing movement of a ship on the waves. Now in order to obtain a just idea of action at the same time to be judiciously satisfied of being in the right in what we do, let us begin with imagining a line formed in the air by any supposed point at the end of a limb or part that is moved, or made by the whole part, or limb; or by the whole body together. And that thus much of movements may be conceived at once is evident, on the least recollection, for whoever has seen a fine arabian war-horse, unback'd and at liberty, and in a wanton trot, cannot but remember what a large waving line his rising, and at the same time pressing forward, cuts through the air; the equal continuation of which, is varied by his curveting from side to side; whilst his long mane and tail play about in serpentine movements. After thus having form'd the idea of all movements being as lines, it will not be difficult to conceive, that grace in action depends upon the same principles as have been shewn to produce it in forms. The next thing that offers itself to our consideration is the force of _habit_ and custom in action; for a great deal depends thereon. The peculiar movements of each person, as the gate in walking, are particularised in such lines as each part describes by the habits they have contracted. The nature and power of habit may be fully conceived by the following familiar instance, as the motions of one part of the body may serve to explain those of the whole.