220 Capt. Forman oti Dr. Young's and La Place's 



tered the Atlantic ; while La Place supposed that it required 

 a day and a half to arrive at the same place. 



It is the nature of fluids to press equally on all sides * ; and, 

 if a portion of its gravity should be taken away from the water 

 in one part of the ocean, the pressure of the other parts will 

 naturally (unless prevented) cause this part to be lifted up, un- 

 til the superior gravit}- of the jiarlicles on one side be balanced 

 bv the greater (juantity on the otlier. So far as I can un- 

 derstand you, for you arc not very ex})licit, this principle forms 

 the groundwork of both your theories : but, at all events, as 

 water, under all circumstances, always tiiUs down when it is 

 deprived of its sujijiort, it nnist be clear that if neither the. 

 moon's attraction nor its centrifugal force can prevent water 

 from falling, they cannot of themselves lift water up ; and, as 

 vou will not allow my principle of expansion to be iin efficient 

 cause, there is no other principle that can, in any way, account 

 for the phenomenon. 



You say " that if the earth were wholly fluid, and the same 

 part of its surface were (ikvai/s tinned towards the moon, the 

 pole of the spheroid being immediately under the moon, the 

 lunar tide would remain stationary, the greatest elevation being 

 at the points nearest the moon and furthest from her, and the 

 greatest depression in the circle equally distant from those 

 points ; f/ie elevation being, hoii^eivr, on account of the smaller 

 surface to rv/iic/i it is confined, t'iince as great as the depression." 



Now, Sir, I have already proved that the moon's attraction 

 cannot lift the waters up, and you have declared that my prin- 

 ciple of expansion is not " well founded." It is fair then to 

 conclude that you account for the rise of those waters which 

 have least gravity, by the pressure of those which have most ; 

 and I admit, that if the same jiart of the earth's surface was 

 alwai/s turned towards the moon {but not ofhci-wise), the pres- 

 sure of the heavier particles would jn'odnce a fall on the one 

 side and a rise on the other, which, added together, would be 

 nearly, but not quite, equal to the j)roportion the loss of gra- 

 vity bore to the dei)tli of water. So far I admit this jirinciple 

 to be good ; but I deny that the elevation will be greater than 

 the fall ; because, if the water be lifted up by pressure, it is 

 evident that the rise on the ope side will be no more than 

 what is just sufficient to make room for the fall on the other. 

 Let the curved line ABC fig. 1. represent the surface of the 

 ocean covering a whole quadrant of the earth's circumference. 



* This, by the way, is caused hj' the etaxfiri/i/, not the slippcrincss, of 

 their particles; ibrif it was not for this prinri|)le of elasticity, the only ef- 

 fect that could he proiliiccd by an increased cravity of the waters would be 

 to bury their lower |)artb deeper in llic bed of the ocean. 



Now 



