194

BOOK VI.

mortised at the lower end a short board ; this has an iron key which engagesa chain, and this chain again a pole-bar. This machine, which draws waterfrom a shaft two hundred and forty feet deep, is worked by thirty-two horses;eight of them work for four hours, and then these rest for twelve hours, andthe same number take their place. This kind of machine is employed at thefoot of the Harz 18 mountains and in the neighbourhood. Further, ifnecessity arises, several pumps of this kind are often built for the purpose ofmining one vein, but arranged differently in different localities varyingaccording to the depth. At Schemnitz, in the Carpathian mountains, thereare three pumps, of which the lowest lifts water from the lowest sump tothe first drains, through which it flows into the second sump ; the intermediateone lifts from the second sump to the second drain, from which it flows intothe third sump ; and the upper one lifts it to the drains of the tunnel, throughwhich it flows away. This system of three machines of this kind is turnedby ninety-six horses ; these horses go down to the machines by an inclined

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