An essay on gold coin [electronic resource] : In which certain methods are laid down to ascertain the quantity and quality of any current piece of gold coin, and by which every species of counterfeit or adulterated coin may be immediately detected. With a description of several new invented instruments of various constructions, to weigh gold either in air with respect to weight, or in water with respect to quality or purry; and which are calculated to answer every purpose required, with respect to accuracy, portability, simplicity, perspicuity, and cheapness; and by which any person may be enabled to judge of the inefficacy of the common scales, and instruments generally used; and informed how to know when an instrument performs well, and is really accurate. Likewise in the course of the work are observations on currency in general, and the present state of our gold coin in particular; with arguments to prove the necessity of a new coinage. By Thomas Hatton, author of a treatise upon clock and watch work.