The happy combination of fortuitous circumstances.

Sir Walter Scott (1771-1832): Answer to the Author of Waverley to the Letter of Captain Clutterbuck. The Monastery.

  The fortuitous or casual concourse of atoms.

Richard Bentley (1662-1742): Sermons, vii. Works, Vol. iii. p. 147 (1692).

  To what fortuitous occurrence do we not owe every pleasure and convenience of our lives.

Oliver Goldsmith (1728-1774): The Hermit. On Woman. Chap. xxi.