of the Neiv Theory of the Tides. 43 



cific gravity be less than that of water : while swimmino- on its 

 surface, by applying a magnet, the ball to which the influence 

 of the magnet is directed will be sensibly elevated, although 

 the magnet has not sufficient power to support the ball in the 

 atmosphere. In this experiment the ball under the influence 

 of the magnet is elevated by the superior gravity of the other 

 ball, on the same principle" {ho-ia is this proved?) " that the 

 flood tide is elevated by the superior gravity of the ebb, for 

 take away the ball that is not influenced by the magnet, and 

 the other immediately sinks ; take away the ebb, and the flow 

 immediately subsides." 



Now I have always been taught to believe, that, in proving 

 tlie possibility of one fact by the acknowledged existence of 

 another, it was necessary for the two cases to be precisely ana- 

 logous ; but what analogy is there between two steel balls con- 

 nected with each other by a stick, and the particles of water, all 

 of which are perfectly independent of each other ? Mr. Rus- 

 sell has very justly observed, that, if we take away the ball that 

 is not influenced by tlie magnet, the other immediately sinks ; 

 and the cause of this is too obvious to require an explanation. 

 So long as the two balls nearly balance each other, the stick 

 is kept in a horizontal position, and they are both supjDorted, 

 not by the power of the magnet, but by the buoyancy of the 

 wood ; but the moment either of the balls is taken away, as the 

 jjower of tlie magnet's attraction is not equal to the gravity of 

 the one that remains, it cannot prevent it from sinking, and the 

 stick, for want of being confined in a horizontal position, is no 

 longer able to support it. Upon the same jirinciple, as the 

 particles of water are not connected with each other by a 

 "wooden lever, the downward pressure of the waters in one part 

 of the world can no more lift up the waters in another, than the 

 downward pressure of one of these steel bails could lift up the 

 other after the stick that connected them was cut in two ; and 

 consequently, so long as the power of the moon's attraction, 

 together with the centrifugal force of the waters, is not equal 

 to the power of the earth's attraction, it is impossible to account 

 for the rising of the waters, except by suj;)posing that they are 

 lifted u}) by the expansion of tlieir own particles. 



If the power of the moon's attraction, by taking off' a portion 

 of the gravity of the particles of water, be not sullicient to pro- 

 chice the cjuantum of expansion in the waters that my theoiy 

 requires, the degree of tlie compressibility of water, even in the 

 deepest parts of the ocean, must be too trifling to deserve any 

 notice ; and, supposing the waters to consist of hard particles, 

 I cannot iinderstantl how a change in the speci/ic giavily of a 

 portion of these particles can produce any alteration in the re- 

 V 2 ' lativc 



