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Assayer's Silver Weights

The richness or purity of silver is either expressed in pennyweights or Tooo. In the first case, it is supposed that the mass of silver to be examined consists of 12 equal parts, called pennyweights; so that if an ingot weighs an ounce, each of the parts will be 1½ of an ounce. Hence, if the mass of silver be pure, it is called silver of 12 pennyweights; if it contain 1½ of its weight of alloy, it is called silver of 11 pennyweights; if 2/2 of its weight be alloy, it is called silver of 10 pennyweights; and so on in proportion for other qualities. It must be observed here, that the assayers give the name pennyweight to a weight equal to 24 real grains, which must not be confounded with their ideal weights.

The assayer's grains are called fine grains. 24 An ingot of fine silver, or silver of 12 penny- 1 weights, contains, then, 288 fine grains; if this ingot contain 288 of alloy, it is said to be silver of 11 pennyweightsand 23 grains; if it contain 288 of alloy, it is said to be 11 pennyweights, 20 grains, &c. The purity of silver is now more frequently expressed in 1000, which admits of greater accuracy.