The Tides in Relation to Geophysical and Cosmic Problems 511 



However, the attraction of the water piled up at the coast at high water 

 causes a further deviation of the pendulum which, with the adopted degree 

 of rigidity of the rocks is computed to be one quarter of the above amount. 

 The total amplitude of the deviation from the plumb line for various distances 

 from the coast is also given in Table 86. In the centre of the continent 



Table 86. Deformation of the surface of the earth by tidal load 



(3140 km distant from the coast) the amplitude would be 012 arc sec. One 

 can see from these values that the effect of the tidal load at H. W. is sufficiently 

 great to disturb the registration of the tides of the solid earth by the horizontal 

 pendulum. It is very difficult to disentangle these two effects, for the reason 

 that the tidal load is different for each station. Darwin gives a good example 

 of the deformation of the earth through the tidal load, which is illustrated 

 in Fig. 210. The Liverpool observatory at Bridston, where the horizontal 



o-o 



0-05 



o-i 



015 



H.W HW. H.W. H.W. 



Fig. 210. Deformation of the earth crust by tidal load observed by the Observatory at Bidston. 



I | I 1 I 



pendulum was set up, is located 2\ km from the sea, at the estuary of the 

 Mersey (see Nature Lond., 1910, p. 427). The larger mass of the water whose 

 weight causes this deformation should be located north-west of the Observatory. 

 Darwin was right in assuming that the deviation was probably caused by the 

 tides in the open sea rather than by the high waters in the estuary. Figure 211 

 shows another example by Takahasi (1929, p. 85) where, near the shore, 

 the disturbance due to the tidal load of high waters can amount to nearly 

 50 times the tides of the solid earth. 



