The merchant's magazine: or, Trades-man's treasury. : Containing, I. Arithmetick ... II. Merchants accompts, ... III. Book-keeping, ... IV. Maxims ... V. The post of letters ... VI. An account of the commodities produced by all countries; ... VII. A merchant or trader's dictionary, ... VIII. Presidents of merchants writings; ... Accomodated chiefly to the practice of merchants and trades-men: but is likewise useful for schools, bankers, diversion of gentlemen, business of mechanicks, and officers of the King's custom and excise. The third edition with improvements