The exceedingly delicate scales were made under the direction of Mr. Peale, who greatly improved on the old ones in use. So precise and sensitive are they that the slightest breath of air affects their accuracy, rendering it necessary to exclude every draft from the room.
Progress in Coining.
The methods of coining money have varied with the progress in mechanic arts, and are but indefinitely traced from the beginning; the primitive mode, being by the casting of the piece in sand, the impression being made with a hammer and punch. In the middle ages the metal was hammered into sheets of the required thickness, cut with shears into shape, and then stamped by hand with the design. The mill and screw, by which greater increase in power, with finer finish was gained, dates back to the Sixteenth Century. This process, with various modifications and improvements, continued in use in the Philadelphia Mint until 1836.
ANCIENT COINING PRESS.
The first steam coining press was invented by M. Thonnelier, of France, in 1833, and was first used in the United States Mint in 1836. It was remodeled and rebuilt in 1858, but in 1874 was superseded by the one now in operation, the very perfection of mechanism, in which the vibration and unsteady bearing of the former press were entirely obviated, and precision attained by the solid stroke with a saving of over seventy-five per cent. in the wearing and breaking of the dies.
STEAM COINING PRESS.