310 BOOK VIII. 



The fine concentrates and fine tin-stone are washed again on this canvas 

 strake. By this method, the canvas lasts longer because it remains fixed, 

 and nearly double the work is done by one washer as quickly as can be done 

 by two washers by the other method. 



The jigging sieve has recently come into use by miners. The 

 metalhferous material is thrown into it and sifted in a tub nearly full of water. 

 The sieve is shaken up and down, and by this movement all the material 

 below the size of a pea passes through into the tub, and the rest remains on the 

 bottom of the sieve. This residue is of two kinds, the metalhc particles, 

 which occupy the lower place, and the particles of rock and earth, which 

 take the higher place, because the heavy substance always settles, and the 

 light is borne upward by the force of the water. This hght material is taken 

 away with a limp, which is a thin tablet of wood almost semicircular in 

 shape, three-quarters of a foot long, and half a foot wide. Before the 

 lighter portion is taken away the contents of the sieve are generally divided 

 crosswise with a limp, to enable the water to penetrate into it more quickly. 

 Afterward fresh material is again thrown into the sieve and shaken up and 

 down, and when a great quantity of metallic particles have settled in the sieve, 

 they are taken out and put into a tray close by. But since there faU into 

 the tub with the mud, not only particles of gold or silver, but also of sand, 

 pyrites, cadmia, galena, quartz, and other substances, and since the 

 water cannot separate these from the metaUic particles because they are all 

 heavy, this muddy mixture is washed a second time, and the part which is 

 useless is thrown away. To prevent the sieve passing this sand again too 

 quickly, the washer lays small stones or gravel in the bottom of the sieve. 

 However, if the sieve is not shaken straight up and down, but is tilted to one 

 side, the small stones or broken ore move from one part to another, and the 

 metaUic material again falls into the tub, and the operation is frustrated. 

 The miners of our country have made ain even finer sieve, which does not 

 fail even with imskilled washers ; in washing with this sieve they have no 

 need for the bottom to be strewn with small stones. By this method the mud 

 settles in the tub with the very fine metaUic particles, and the larger sizes of 

 metal remain in the sieve and are covered with the valueless sand, and this 

 is taken away with a limp. The concentrates which have been collected 

 are smelted together with other things. The mud mixed with the very fine 

 metaUic particles is washed for a third time and in the finest sieve, whose 

 bottom is woven of hair. If the ore is rich in metal, aU the material which 

 heis been removed by the Ump is washed on the canvas strakes, or if the ore 

 is poor it is thrown away. 



I have explained the methods of washing which are used in common for 

 the ores of many metals. I now come to another method of crushing ore, 

 for I ought to speak of this before describing those methods of washing which 

 are pecuhar to ores of particular metals. 



In the year 1512, George, the iUustrious Duke of Saxony^*, gave the over- 



'*George, Duke of Saxony, surnamed " The Bearded," was born 1471, and died 1539. 

 He was chiefly known for his bitter opposition to the Reformation. 



