This insoluble residue, called ` nai chai ' (opium dirt), is the perquisite of the head boiling coolie, who finds a ready market for it in Canton, where it is used for adulterating, or rather in manufacturing, the moist inferior kinds of prepared opium.
A large fleet is engaged in the fishery; and a great number of factories extract the oil for tanning and currying, and for adulterating other more expensive oils, and manufacture the refuse into a valuable guano.
I am not quite sure that this method of weighting was not first used by the throwsters, as sugar is known to have been used for adulterating and loading gum silk for a very long time, and then the idea was afterwards applied to silk after the dyeing operations.