BOOK X.

456

ashes fall from the burnt wood, which is supported by iron rods, arranged toform a grating. The middle chamber is two feet high, and the wood is pushedin through its mouth. The wood ought to be oak, holmoak, or turkey-oak,for from these the slow and lasting fire is made which is necessary for thisoperation. The upper chamber is open at the top so that the pots, for whichit has the depth, may be put into it; the floor of this chamber consists of ironrods, so strong that they may bear the weight of the pots and the heat of thefire ; they are sufficiently far apart that the fire may penetrate well and mayheat the pots. The pots are narrow at the bottom, so that the fire enteringinto the space between them may heat them ; at the top the pots are wide,so that they may touch and hold back the heat of the fire. The upper partof the furnace is closed in with bricks not very thick, or with tiles and lute,and two or three air-holes are left, through which the fumes and flames mayescape.

The gold granules or leaves and the cement, alternately placed in the pots,are heated by a gentle fire, gradually increasing for twenty-four hours, if thefurnace was heated for two hours before the full pots were stood in it, and ifthis was not done, then for twenty-six hours. The fire should be increasedin such a manner that the pieces of gold and the cement, in which is thepotency to separate the silver and copper from the gold, may not melt, for inthis case the labour and cost will be spent in vain ; therefore, it is ample tohave the fire hot enough that the pots always remain red. After so manyhours all the burning wood should be drawn out of the furnace. Then therefractory bricks or tiles are removed from the top of the furnace, and theglowing pots are taken out with the tongs. The lids are removed, andif there is time it is well to allow the gold to cool by itself, for then there isless loss ; but if time cannot be spared for that operation, the pieces of goldare immediately placed separately into a wooden or bronze vessel of waterand gradually quenched, lest the cement which absorbs the silver shouldexhale it. The pieces of gold, and the cement adhering to them, when cooledor quenched, are rolled with a little mallet so as to crush the lumps and freethe gold from the cement. Then they are sifted by a fine sieve, which isplaced over a bronze vessel; in this manner the cement containing thesilver or the copper or both, falls from the sieve into the bronze vessel, and thegold granules or leaves remain on it. The gold is placed in a vessel andagain rolled with the little mallet, so that it may be cleansed from the cementwhich absorbs silver and copper.

The particles of cement, which have dropped through the holes of thesieve into the bronze vessel, are washed in a bowl, over a wooden tub, beingshaken about with the hands, so that the minute particles of gold which havefallen through the sieve may be separated. These are again washed in alittle vessel, with warm water, and scrubbed with a piece of wood or a twigbroom, that the moistened cement may be detached. Afterward all the goldis again washed with warm water, and collected with a bristle brush, and shouldbe washed in a copper full of holes, under which is placed a little vessel.Then it is necessary to put the gold on an iron plate, under which is a vessel,