so be done for two or three hours. Then the upper wood is taken off, and the pestle washed in the same water with a pencil. Afterwards the mill is taken up, and the gold, with the water, is stirred to the bottom with the pencil, and is left a little, until the grosser part subsides; the water is presently poured into a very clean basin, and whatever gold comes away with the water is ground. Replacing the water and the pestle, and wood above being placed, again it is milled in the same way as before, until it altogether comes away with the water. In the like manner are ground silver, brass, and copper. But gold is ground most carefully, and must be lightly milled; and you must often inspect it, because it is softer than the other metals, that it may not adhere to the mill or the pestle, and become heaped together. If through negligence this should happen, that which is conglomerate is scraped together and taken out, and what is left is milled until finished. Which being done, pouring out the upper water with the impurities from the basin, wash the gold carefully in a clean shell; then pouring the water from it, agitate it with the pencil, and when you have had it in your hand for one hour, pour it into another shell, and keep that very fine part which has come away with the waters. Then again, water being placed with it, warm it and stir it over the fire, and, as before, pour away the fine particles with the water, and you may act thus until you shall have purified it entirely. After this wash with water the same refined part, and in the same manner a second and a third time, and whatever gold you gather mix with the former. In the same way you will wash silver, brass, and copper. Afterwards take the bladder of a fish which is called _huso_ (sturgeon), and washing it three times in tepid water, leave it to soften a night, and on the morrow warm it on the fire, so that it does not boil up until you prove with your finger if it adhere, and when it does adhere strongly, the glue is good. CHAPTER XXXI. HOW GOLD AND SILVER ARE LAID IN BOOKS.