Definition of "effectual"

Redoubling, then, the active energy of his thrusts, favoured by the fervid appetite of my motions, the soft oiled wards can no longer stand so effectual a picklock, but yield, and open him an entrance.

1749, [John Cleland], “(Please specify the letter or volume)”, in Memoirs of a Woman of Pleasure [Fanny Hill], London: […] G. Fenton [i.e., Fenton and Ralph Griffiths] […]

In the living state, the body is observed to […] adopt most effectual measures for the permanent continuance of its species.

1822, John Barclay, chapter I, in An Inquiry Into the Opinions, Ancient and Modern, Concerning Life and Organization‎, Edinburgh, London: Bell & Bradfute; Waugh & Innes; G. & W. B. Whittaker, section I, page 1