It must launch itself in the ocean of air, and must extract from that air, by means of its travelling surfaces - however fashioned and however applied - the recoil or resistance necessary to elevate and carry it forward.
The Slavonic peoples, whose territories then extended to the Elbe, and embraced the whole southern shore of the Baltic, were beginning to recoil before the vigorous impetus of the Germans in the West, who regarded their pagan neighbours in much the same way as the Spanish Conquistadores regarded the Aztecs and the Incas.
In this aversion to a purely or mainly intellectual training may be traced a recoil from the systematic metaphysics of Plato and Aristotle, whose tendency was to subordinate the practical man to the philosopher.
These machines, which are driven by compressed air, are very handy in use, as the height and direction of the cut may be readily varied; but the work is rather severe to the driver on account of the recoil shock of the piston, and an assistant is necessary to clear out the small coal from the cut, which limits the rate of cutting.
Anything different doesn't seem as human to us and we instinctively recoil from it.
Of the energy exerted by the powder in exploding will be employed in propelling the ball, and ih in producing the recoil of the gun, provided the gun up to the instant of the balls quitting the muzzle meets with no resistance to its recoil except the friction of the ball.
And if the idea of peril so much enhances the popular conceit of the soldier's profession; let me assure ye that many a veteran who has freely marched up to a battery, would quickly recoil at the apparition of the sperm whale's vast tail, fanning into eddies the air over his head.
The French struggled gallantly to the close: but now a long succession of their leaders - Junot, Soult, Victor, Massena, Marmont, Joseph - had been in turn forced to recoil before 'Wellington; and while their troops fought henceforward under the depressing memory of many defeats, the Allies did so under the inspiriting influence of great successes, and with that absolute confidence in their chief which doubled their fighting power.
The figure-of-8 and kite-like action of the wing referred to lead us to explain how it happens that the wing, which in many instances is a comparatively small and delicate organ, can yet attack the air with such vigour as to extract from it the recoil necessary to elevate and propel the flying creature.
In the opening lines of the second and third books we can mark the recoil of a humane and sensitive spirit from the horrors of the reign of terror which he witnessed in his youth, and from the anarchy and confusion which prevailed at Rome during his later years.