46 Captain Forman's Defence of 



carry them off. Facts, however, when they can be found, are 

 the best arguments ; and, m spite of Mr. Russell's objections,! 

 shall make use of a handful of water in order to prove that both 

 of these opinions are diiectly the reverse of what is really the 

 fact If we take up a handful of water at the time the tides 

 are rising, it must be evident that, as this water is brought 

 nearer the moon and carried further from the earth, the power 

 of the moon's attraction must be increased and the power of 

 the earth's diminished ; and consequently, if the power of the 

 moon's attraction had been sufficient to lift the v.aters up in the 

 first place, it would certainly be sufficient to prevent them from 

 falling when they were brought so much nearer to it. The 

 same argument holds equally good with respect to the notion 

 of the waters being raised by a centrifugal force ; for as a drop 

 of water upon the tgp of a high mountain travels through a 

 much greater quantity of space in the same time, its centrifugal 

 force must be considerably greater, while the jiower of the 

 earth's attraction to restrain it wUl be proportionably less, than 

 it is in any part of the ocean ; and if this centrifugal force is 

 not able Xo prevent 'water from falling when its power is great- 

 est, liow is it possible for it to Uft xirnter up in those places 

 where its power is so much less ? Wherever we have the op- 

 portunity of making the experiment, we always find that water 

 falls downward when the support upon which it rests is taken 

 away. It is evident then, that when the tides are rising, the 

 waters must be pushed upwards by some power below ; and, 

 unless we can suppose that the bed of the ocean is lifted up by 

 the moon's attraction, (when it has not power to lift a grain of 

 sand upon the earth's surface,) there is no power that can pro- 

 duce this eifect besides expansion in their own particles. 



Philosophers, upon what principle I cannot imagine, have 

 latterly conceived the notion, that, in the deep parts of the 

 ocean, the waters are agitated and put in motion by a centri- 

 fugal force, occasioned by the earth's revolving lound the 

 common centre of gravity of the earth and moon ; and that it 

 is this agitation that produces the rishig of the tides*. This 

 opinion however is grounded upon no analogy, and is in direct 

 opposition to evident facts. On every part of the earth's sur- 

 face, in lakes and ponds, or wherever we may choose to place 

 a drop of water, the centrifugal force, occasioned by the earth's 

 motion, has not power to produce the least sensible rise ; and 

 as, the deeper the waters get, their centrifugal force wUl be so 

 much diminished, while the power of the earth's attraction 



* See Dr. Young's Natural Philosophy, and an article, on Ciithbert's 

 New 'J'licory of the Tiilcs, in (he 4th vohlme of the Quarterly Review. 



must 



