Mr. A. Tylor on Tides and Waves. 219 



periodicity about the alternation of land and water surfaces, 

 particularly in the Carboniferous period, which might be ex- 

 plained by slow changes in long intervals of the disposition of 

 the solid and fluid internal substance of the earth with regard 

 to and about its centre. 



A slow circulation of an eccentric mass of fluid may occur in 

 the interior of the earth, and gases may periodically pass from one 

 part of the solid portion to another, their place being supplied 

 by fluids, attracting the ocean unequally. 



Unequal attraction from variable subterraneous inequalities 

 would affect different points of the surface and raise the water- 

 level on one part for long periods and depress it on alternate and 

 opposite points to an equal extent. The theory of inconstancy 

 of rainfall and of fluctuation of the sea-level in geological periods 

 is gaining ground since I first advanced these views (in 1853) in 

 this Journal, in a paper entitled " Fluctuations of the Sea-level 

 in stated Periods of Time." 



We must not gauge our interpretation of nature by the pre- 

 sent temperature, rainfall, or tide-gauges, but from the actual 

 evidence presented in the strata themselves. 



In conclusion, if all the lines of lunar attraction M /} M /y , &c. 

 (fig. 4, PI. IV.) were continued through the earth without deflec- 

 tion from a straight line, then there could be only one lunar tide in 

 the twenty-four hours ; for all the water on one side of the axial 

 line, E C W or half the globe, moving in the direction of the ro- 

 tation of the earth, would be accelerated, and all the water in the 

 other half,E B W, of the globe would be retarded, as the attraction 

 of the moon in that half would be contrary to the direction of the 

 rotation of the earth. The fact of the tides occurring every twelve 

 hours is a proof that the view I have put forward of the deflec- 

 tion of the attracting rays in their passage through the earth is 

 a correct one. The twelve-hour tides on the opposite side of the 

 earth to the moon are physical proofs that attraction -rays are de- 

 flected. If not, there could be no such effect of attraction on the 

 ocean as is shown by the twelve-hour tide. The theoretical 

 differences of one fifteenth of the height of alternate tides I 

 believe accord with observation, taking the average of the world. 



According to Professor Stokes, any solution of a problem that 

 satisfies all the conditions must be the true one. I believe 

 the solution suggested in this letter conforms entirely to the 

 facts, and that the deflection-theory, now, I believe, first pro- 

 posed, is true. Yours truly, 



A. Tylor. 



P.S. With regard to the new equations to the flow of water 

 in page 205, 1 use coefficients for different materials of channels : 

 see note to PI. III. fig. 3. 



