22$ Capt. Formau on Dr. Young's and La Place's 



to reach the distance of two hundred miles, and consequently 

 would be high water at the Land's End exactly at the time set 

 down in the Tide-table. Now if it should be found that, at the 

 distance of more than two hundred miles from the Land's 

 End, ships are in the habit of striking soundinjrs, it would be 

 evident that my theory was erroneous ; but if they cannot get 

 soundings in any part of the woi'ld, at those distances from the 

 shore where my theory indicates the tides are produced, this 

 circumstance will amount to a demonstrative proof that my 

 theory must be true: for it is morally impossible that a false 

 theory can always be right by chance. 



Ao'ain, I have proved (fig. 1 ) that, if the waters were lifted 

 iip by pressure, the elevation would be equal to only the fall ; 

 whereas, you have acknowledged yourself, and the fact is easily 

 proved, that it ought to be at least twice as great. Let us now 

 see whether my theoi-y of expansion will account for this phae- 

 nomenon ; and if it will, in what way can you account for a false 

 theory's correspondii^.g, in every particular, with the phaeno- 

 mena in question? Let L M (fig 3.) represent the level of the 

 ocean, with the moon vertical at M, or, rather, about two de- 

 grees beyond it, and LH the waters gi-adually lifted up by ex- 

 pansion, from the point where the moon has no influence to the 

 point where her influence is greatest. Now it is evident, that 

 the higher the waters are raised the more rare they will be- 

 come ; and, as the denser parts of the fluid must necessarily 

 press upon the rarer, the pressure produced in this way will 

 occasion an additional rise on the one side and a corresponding 

 fall on the other. Here, Sir, you will observe, that there is no 

 impediment to prevent this pressure from taking effect, because 

 the waters actually do become rarer, and the pressure takes 

 place at the same moment with the expansion. The dotled 

 line ///, in the above figure, represents the elevation and fall pro- 

 duced by this pressure ; and, though it may be difficult, if not 

 impossible, to calculate the exact proportion, it is evident that 

 the elevation will be so much greater than the fall, as the waters 

 are lifted up in the first place by expansion, independently of 

 pressure. 



Now, Sir, suppose you had occasion to pass through a wild 

 and intricate country, where you had never travelled before : 

 it is possible that a stranger might put you in the right road by 

 accident ; but if thci e were a great number of subsequent turn- 

 ings, your guide could not always go right, unless he was well 

 acquainted with the way ; and, by the same rule, if my theory 

 was false, it might, by pure ivecident, agree with one or two iso- 

 lated iacts ; but it is impossible that it could so entirely coincide 

 with all the most minute phasnomena, unless these phajnomena 



were 



