Archdeacon Pratt on the effect of 



to prove that the crust is very thick, at least 800 or 1000 miles ; and this 

 result, I understand, has been recently confirmed by Professor W. Thomson 

 in a paper " On the Rigidity of the Earth." 



18. These theoretical considerations receive, I think, some confirmation 

 from an examination of the calculated deflection of the plumb-line at sta- 

 tions near the sea-shore. It is for this reason that I have collected the 

 thirteen examples from the Anglo-Gallic and Russian Arcs in paragraph 

 15, all of which are near the coast. The evidence they furnish, however, 

 is not to be compared in weight with that of the Indian Arc, already con- 

 sidered. In some instances the local attraction of the surrounding country 

 and of the ocean for a certain distance has been calculated, as already 

 stated. These results I will take into account, except the allowances for 

 the ocean as noted at the end of paragraph 15, which I deduct in the fol- 

 lowing arrangement of the stations. 



The Stations at which the Deflection is towards the Land, 



o , Deflection. „ 



(1) Barcelona, lat. 41 23, S.E. coast of Spain, -f 2*22 



(2) Dunkirk, „ 51 2, N.N.W. France, -0-84 



(7) Blackdown, „ 50 41, S. „ Dorset, -f 2-76 



(9)Cowhythe, „ 57 41, N. „ Banff, -3-81 +0-70 = — 3-11 



(10) BenHutig, „ 58 33, N. „ Sutherland, - 1-24 + 0-64=— 0*60 



(12) Tornea, „ 65 50, S. „ Lapland, +4-69 



The Stations at which the Deflection is towards the Sea. 



o , Deflection. 



(3) HighPortCliff,50 36, S. coast of Isle of Wight,-2-01 -0-27== -2*28 



(4) Week Down, 50 36, „ „ -l-73-0-27=-2-00 



(5) BonifaceDown,50 36, „ „ — 1-96-0-27=-2-23 



(6) Dunnose, 50 37, „ „ —l'46-0'27=-l'73 



(8) BurleighMoor, 54 34, N. coast of Yorkshire, +0-40 + 0-39= -f 079 



(11) Saxavord, 60 50, N. „ Unst, +0-41 



(13) Fuglenoes, 70 40, N. „ Finraark, +M3 



The theory I have proposed, that contraction of the crust has formed the 

 basins in which the sea has settled, can hardly be expected to apply so 

 completely to such confined sheets of water as the Mediterranean south 

 of Spain, and the Gulf of Bothnia. Here there may be an actual defici- 

 ency of attracting matter in the water, not altogether compensated for by 

 increased density of the crust below. These hollows may have been formed 

 during the breaking up of the crust and subsequent removal of portions by 

 currents, and not chiefly by the contraction of the crust. Thus the deflec- 

 tions at the stations (1) and (12) towards the land may be sufficiently 

 accounted for, even if the land about Barcelona and Tornea does not rise 

 sufficiently high to produce them. The deflection at station (2) is small. 

 It seems probable that even if the North Sea has been produced according 



