BOOK VIII. 295 



method of grinding requires the millstone to be now raised and now 

 lowered, the timber in whose socket the iron of the pinion axle revolves, rests 

 upon two beams, which can be raised and lowered. 



There are three mUls in use in miUing gold ores, especially for quartz" 

 which is not lacking in metal. They are not all turned by water-power, 

 but some by the strength of men, and two of them even by the power 

 of beasts of burden. The first revolving one differs from the next only 

 in its driving wheel, which is closed in and turned by men treading it, or by 

 horses, which are placed inside, or by asses, or even by strong goats ; the 

 eyes of these beasts are covered by linen bands. The second mill, both 

 when pushed and turned round, differs from the two above by having an 

 upright axle in the place of the horizontal one ; this axle has at its lower end 

 a disc, which two workmen turn by treading back its cleats with their feet, 

 though frequently one man sustains all the labour ; or sometimes there 

 projects from the axle a pole which is turned by a horse or an ass, for which 

 reason it is called an asinaria. The toothed drum which is at the upper end 

 of the axle turns the drum which is made of rundles, and together with it the 

 mUlstone. 



The third mill is turned round and round, and not pushed by hand ; but 

 between this and the others there is a great distinction, for the lower 

 mUlstone is so shaped at the top that it can hold within it the upper mill- 

 stone, which revolves around an iron axle ; this axle is fastened in the 

 centre of the lower stone and passes through the upper stone. A workman, 

 by grasping in his hand an upright iron bar placed in the upper millstone, 

 moves it round. The middle of the upper millstone is bored through, and 

 the ore, being thrown into this opening, falls down upon the lower millstone 

 and is there ground to powder, which gradually runs out through its opening ; 

 it is washed by various methods before it is mixed with quicksUver, 

 which I will explain presently. 



Some people build a machine which at one and the same time can crush, 

 grind, cleanse, and wash the gold ore, and mix the gold with quicksilver. 

 This machine has one water-wheel, which is turned by a stream striking its 

 buckets ; the main axle on one side of the water-wheel has long cams, which 

 raise the stamps that crush the dry ore. Then the crushed ore is thrown 

 into the hopper of the upper millstone, and gradually faUing through the 

 opening, is ground to powder. The lower millstone is square, but has a round 

 depression in which the round, upper millstone turns, and it has an outlet 

 from which the powder falls into the first tub. A vertical iron axle is dove- 

 tailed into a cross-piece, which is in turn fixed into the upper millstone ; 

 the upper pinion of this axle is held in a bearing fixed in a beam ; the dnmi 

 of the vertical axle is made of rundles, and is turned by the toothed drmn 

 on the main axle, and thus turns the millstone. The powder falls continually 

 into the first tub, together with water, and from there runs into a second tub 

 which is set lower down, and out of the second into a third, which is the 

 lowest ; from the third, it generally flows into a small trough hewn out of a 



^^Lapidibus liquescentibus. (See note 15, p. 380). 



