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124 us; this Matter goes from West to East, since all the Planets are carried from West to East. Thus from Hypothesis to Hypothesis, from one Appearance to another, Philosophers have imagin'd a vast Whirlpool of subtile Matter, in which the Planets are carried round the Sun: They also have created another particular Vortex which floats in the great one, and which turns daily round the Planets. When all this is done, 'tis pretended that Gravity depends on this diurnal Motion; for, say these, the Velocity of the subtile Matter that turns round our little Vortex, must be seventeen Times more rapid than that of the Earth; or, an case its Velocity is seventeen Times greater than that of the Earth, its centrifugal Force must be vastly greater, and consequently impell all Bodies towards the Earth. This is the Cause of Gravity, according to the Cartesian System. But the Theorist, before he calculated the centrifugal Force and Velocity of the subtile Matter, should first