Definition of "quickening"

If the following guide lose his distance from the one leading (which can only happen by his own fault), he will correct himself by slightly lengthening or shortening a few steps, in order that there may not be sudden quickenings or slackenings in the march of his platoon.

1861, United States. War Dept, U.S. Infantry Tactics, page 124

It resembled them in the sense that it was not ended, when it was past, but continued to unfold, in Watt's head, from beginning to end, over and over again, the complex connexions of its lights and shadows, the passing from silence to sound and from sound to silence, the stillness before the movement and the stillness after, the quickenings and retardings, the approaches and the separations, all the shifting detail of its march and ordinance, according to the irrevocable caprice of its taking place.

1953, Samuel Beckett, Watt, Olympia Press

It may indeed be said that these days brought on a high quickening of Maisie's direct percptions, of her sense of freedom to make out things for herself.

1897 October 16, Henry James, What Maisie Knew, Chicago, Ill., New York, N.Y.: Herbert S. Stone & Co.