State of the British and French colonies in North America : with respect to number of people, forces, forts, Indians, trade and other advantages : in which are considered, I. The defenceless condition of our plantations, and to what causes owing : II. Pernicious tendency of the French encroachments, and the fittest methods of frustrating them : III. What it was occasioned their present invasion, and the claims on which they ground their proceedings : with a proper expedient proposed for preventing future disputes : in two letters to a friend