Mr. A. Tylor on Tides and Waves. 213 



the earth, except when modified in velocity to a very small ex- 

 tent by the attraction of the celestial bodies, producing the tides. 

 The two cases are not parallel, and the diagram mentioned by 

 Herschel is certainly not applicable to the tides at all. The 

 oceanic water has no tangential force independent of the earth ; 

 for two points in the ocean, reaching 180°, opposite to each other 

 are at the same distance from the centre of the earth, and are in 

 exact equilibrium if the difference of tidal action is left out of 

 consideration. I think the authors have not taken into consi- 

 deration the fact that the rays of attraction from the moon to 

 the water, when the water is screened from the moon by the 

 earth, would pass through the earth, in order to reach the oppo- 

 site side, not in a straight line. They would not only lose force of 

 course as the square of the distance increased, but I think no 

 ray or vibration or impulse or line of attractive force could fall 

 upon or pass through a curved body such as the earth at an acute 

 angle without being in some way deflected or diverted from its 

 direct course in passing through the earth to water on the other 

 side ; and the reverse is true. I believe a vibration of any kind, or 

 attraction-ray, would have to be modified in its direction or bent 

 at the point of contact, so as to enter the surface of the earth at a 

 right angle to ajtangent of the curve at the point, as shown in fig. 4. 



My own view (PI. IV. fig. 4) shows slack water at the turn 

 of the tide both near high and near low water; but of course these 

 events do not always coincide. When the luni-solar attraction-rays 

 fall near A and B (fig. 4, PI. IV.), they are evidently deranged and 

 deflected so as to produce very little effect ; in fact the state of 

 the tide near those points is what might be called bordering on 

 motion, which state accords with observation. Although the angle 

 M / P / R / is only 1"07, or two thirds of the angle M^R,,, yet the 

 actual effect in producing tidal motion is much less than that 

 proportion. For at P the tidal motion is being reversed, and 

 the speed of the flowing tide has to be created from slack water; 

 while at P /; the effect of attraction from M n is to accelerate the 

 tide then moving freely and in the same direction as it has been 

 between P y and P yy , and also in the line of the earth's rotation. 

 The actual effect in velocity theoretically is quite four times as 

 much in the half hour near P /y as at that near P y ; and this accords 

 with observation. The angle of the resultant R y is found thus. 

 The angle M ; P y C is 88° 30' 4" = 318604 seconds. 



The force M y P y is to CP, as 1 to 295,520; .-. the angle 



M y P y R y , the resultant, equals ' = 1"*07. In the same 



manner the angle M y/ P /y R w = l"-66. The depth of the Atlantic 

 (five miles) favours movement very much, as there is room for the 

 force in the direction A R /; to be transferred easily into the direc- 



