Theories of the Tides. 225 



isure does not produce any sensible rise in the waters; and, as 

 it does not, we have certainly no grounds to suppose that the 

 comparatively trifling pressure occasioned by the moon's attrac- 

 tion is sufficient to produce a rise in the waters of several fa- 

 thoms. 



The phsenomena of the tides in every respect are totally dis- 

 similar to the effects that must necessarily be produced by pres- 

 sure ; and this fact alone, even if the impossibility had not been 

 made good, would be quite sufficient to prove that the tides are 

 not produced by pressure. I have also proved that your and 

 Laplace's theories are at variance with facts, and therefore 

 cannot possibly be true; and I shall now show, that the neces- 

 sary consequences of my theory correspond in every particular 

 with the phasnomena that really take place in nature : and if 

 all this, taken together, do not amount to a sufficient proof that 

 my theory is true, I am at a loss to understand how any thing 

 in philosophy can be proved, or why we should set a greater 

 value upon the opinions of a Newton, than upon the wild and 

 frantic conceptions of the most fanciful enthusiast. 



As the sum of the expansion of a sufficient number of parti-, 

 cles will amount to several fathoms, while the sum of the ex- 

 pansion of a very few will be imperceptible, my principle of ex- 

 pansion necessarily requires that there should be a sufficient 

 depth of water in the neighbourhood of any projecting cape 

 where the tide first makes its appearance, and that the moon 

 should be vertical, or nearly vertical, over that place at the time 

 of high water. Now, if it should be found that the time which 

 my theory necessarily requires for the tide to arrive at the coast 

 afi:er it has been produced in this deep water, should, as far as we 

 are capable of proving it, exactly correspond with facts, it will 

 furnish a strong presumption that my theory is true ; and I am 

 very willing to allow its reception to depend upon this proof. 



It appears by the Tide-table now before me, that it is high 

 water at the Land's End four hours and a half after the moon 

 lias passed the meridian. Now, if we suppose this tide to be 

 produced at about two hundred miles to the south-west of the 

 Land's End, the moon will be on the meridian at that place 

 about sixteen minutes after she has passed the meridian of the 

 Land's End : and, supposing the ocean in this place to be seven 

 or eight miles deep, and the pressure to move at the rate of 

 about fifty miles an hour, it will take ten or twelve minutes 

 afterwards for the tide to arrive at its full height. It would 

 be high water then at this place about half an hour after the 

 moon had passed the meridian of the Land's End ; and, sup- 

 posing the tide to advance at the rate of fifty miles an hour, 

 which it does in the Channel, it would require just four hours 



Vol.61. No. 299. March 1823. Ff to 



