Page:Popular Science Monthly Volume 11.djvu/601

Rh manufactory, in shape of flat river-pebbles, all of which are polished on the flat surface, just as the digging edges of the stone spades are by use. Cement thus compressed would be too hard to take the perfect impression of the cloth bandage; but a thin layer, or even a



wash, of river-silt or mud would take it, and at the same time prevent the cloth adhering to the vessel; and, when required to be removed, a slight surface-moistening would accomplish the object without