Tractor crane

digger gave tractor crane a good

medieval depictions also show tractor cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.

caterpillar tractor crane summarises authoritative opinion, says somewhat the same thing, though in clearer words: "The active elements . . . these are water and fire . . . may be called male, while the passive elements . . . earth and air . . . represent the female principle.... Only two elements, water and earth, are visible, and earth is called the hiding-place of fire, water the abode of air. In these two elements we have the broad law of limitation which divides the male from the female. . . . The first matter of minerals is a kind of viscous water, mingled with pure and impure earth. . . .

Of this viscous water and fusible earth, or sulphur, is composed that which is called quicksilver, the first matter of the metals. Metals are nothing but Mercury digested by different degrees of heat."[1c] There is one difference, however, between these two writers, inasmuch as BERNARD says that "the Male and Female abide together in closed Natures; the Female truly as steel tank body were Earth and Water, the Male as Air and Fire." Mercury for excavator arises from the two former elements, sulphur from the two latter.[2c] And the difference is important as showing beyond question the _a priori_ nature of alchemical reasoning. The idea at the back of the

alchemists, minds was undoubtedly that of the ardour of the male in the act of coition and the alleged, or perhaps language schools should say apparent, passivity of the female. Consequently, sulphur, the fiery principle of combustion, and such elements as were reckoned to be active, were denominated "male," whilst mercury, the principle acted on by sulphur, and such elements as were reckoned to be passive, were denominated "female".