John Clerk, a British naval tactician, born at Eldin, Scotland, about 1730, died in 1812. He was a country squire who studied naval science, and is said to have disclosed in 1771) his discovery of a new mode of operation for breaking the enemy's line in naval battle, which was successfully applied by Rodney in his victory over the French under De Grasse in the West Indies, April 12, 1782, and subsequently by other British commanders in many memorable encounters. Sir Howard Douglas, whose father had served under Rodney, contested Clerk's claim to the discovery; and it was asserted by others that Clerk had taken his "Essay on Naval Tactics" (privately circulated in 1782; republished 1790-'98, with additions; new ed., 1804; French translation by Lescalier, 2 vols., 1797) from Father Paul Hoste's L'Art des armees navales (Lyons, 1696 and 1727). The fact of his having never been in the naval service, or even at sea, strengthened his opponents; but Clerk's claim to the invention is generally regarded as substantiated.