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LX.— ON THE EFFECT OF CONTINENTAL LAND IN ALTEE- 

 ING THE LEVEL OF THE OCEAN. By EDWAED 

 HULL, LL.D., F.E.S., &c, Director of the Geological 

 Survey of Ireland. 



[Read, March 23, 1887.] 



When looking into the work of Professor Edward Suess, " Das 

 Antlitz der Erde," x I was much surprised on lighting on a passage 

 in which the author appears to adopt the view, that in some cases 

 the level of the surface of the ocean along the margin of a conti- 

 nent maybe as much as 1100 metres (or 3380 Parisian feet) above 

 that of the surface along the shores of a mid-oceanic island ; that is 

 to say, so much further from the centre of the earth in the same 

 parallel. This statement is founded on a formula adopted by 

 Fischer 2 for the determination of the relative levels by means of 

 oscillations of the daily second's pendulum at different stations 

 along a continental coast, and a mid-oceanic island, to the effect 

 that the amount in metres will be nearly 122 times the difference 

 in the number of such oscillations. No special stations are men- 

 tioned ; but he takes an example where the difference in the num- 

 ber of oscillations amounts to nine, giving the result of 1100 metres 

 (in round numbers), above stated. In any case this is sufficiently 

 startling, and, if correct, would be a great advance on the views 

 generally held on this subject. If correct, even approximately, it 

 is clear that large portions of continental lands are submerged 

 which would otherwise be uncovered ; while many islands owe their 

 existence as such to the abnormal lowering of the ocean surface at 

 a distance far removed from continents. 



To some extent this is true ; but the question arises, to what 

 extent even in extreme cases. 



As the length of the second's pendulum is proportionate to the 



1 " Das Antlitz der Erde," 1st Abteil., p. 3 (1883). 



2 Fischer, " Untersuchungen liber die Gestalt der Erde " (li 



