Note 269 — THE CATHOLIC WORLD. VOL. XVIII., No. 108.—MARCH, 1874.[249] (continued 2)

This limitation is necessity. A stone thrown up vertically soon loses its vis viva without compensation. The case is one in which there is no impact. An imponderable body, as luminiferous æther, if it forms, as it is most probable, an unresisting medium, acquires vis viva without interfering with the vis viva of the celestial bodies.