270 THE AEGUMENT FOR SOLIDITY. 



a further reduction owing to the fact that a solid earth could 

 not be absolutely rigid ; if as rigid as steel, the tide should 

 reach about two-thirds of its equilibrium value. 



Introducing the actual figures, we have for the case of a 

 solid earth : — 



(1) Due to equilibrium theory ; the fortnightly tide at 

 the equator should range about '07 ft. above and below a 

 mean level. 



(2) Applying Professor Darwin's kinetic correction, the 

 range should only be '035 ft. 



(3) For an earth no more elastic than steel, the range 

 would be '023 ft. {i.e. about \ in.). 



This small amount is the greatest height the tide could 

 reach at the equator : at places farther North and South, the 

 tide will be smaller, until, at about 35^ latitude, the height 

 will be zero. 



It is clear, then, that the determination of the fortnightl}^ 

 tide must be made between the equator and the thirty-fifth 

 j)arallel ; that the ocean should be unencumbered and deep ; 

 that the water near the observatory should not be shallow ; 

 and that the observatorj^ should not be within a rapidly 

 narrowing estuary. 



All these desiderata point to the Indian ports as by far 

 the best suited to the purpose ; and, at Lord Kelvin's sug- 

 gestion, tidal stations have been set up at many points along 

 the coasts of Burma, India, and Cejdon, and the results 

 analyzed, with the object of determining the rigidity of the 

 earth. 



Colonel Baird, H.E., who for several years was in charge 

 of these observations, has kindly obtained for me the com- 

 plete tidal determinations at each of the Indian ports up to 

 the end of the year 1894. These results are given in feet, 

 and represent the average, throughout each j^ear, of the 



