J. Starlde Gardner — Permanence of Continents and Oceans. 243 



exceptionally rough weatber. We have generally to trust to founda- 

 tions and well-borings near the coast, and these, as far as I am 

 acquainted with them, have invariably shown that our sea-shores are 

 steadily sinking. If this were not so, our land would be surrounded 

 by extensive shoals of uniform depth, for the whole of the sediments 

 from the wasting of the shore are thrown down almost entirely upon 

 a belt 30 miles wide. The moving power of waves is not felt to a 

 greater depth than forty feet, tides appear to have no permanent 

 action in removing sediment, and shore currents of sufficient power 

 are local and merely cut channel-ways. The rapidity with which silt 

 accumulates may be seen by the manner in which wrecks become lost 

 to view, and in the discolouration of the sea during rough weather pro- 

 daced by particles from the shore held in suspension. This shore 

 deposit does not find its way to the depths of the ocean, and if its 

 constant accumulation is not balanced by subsidence, what becomes of 

 it ? ^ A glance moreover at any stratified rock composed of littoral 

 deposits, will show from its thickness, which often exceeds the depth 

 of water in which it is supposed to have been deposited, that it 

 must have been deposited in a subsiding area. No conclusion but 

 this can be drawn in working through our Eocenes, and it is suffi- 

 ciently obvious that no thick littoral deposit can take place in an 

 area of elevation. 



If the theory that sedimentation directly causes subsidence is 

 pushed still further, we discover a physical reason for the per- 

 manence of Ocean basins. If permanent, deposition must have 

 been continuous since Palaeozoic times, and would to a large 

 extent have filled in even the very greatest depths of the ocean, 

 unless compensated by constant and gradual depression. The mean 

 of four experiments made on the " Challenger " Expedition, deter- 

 mined the quantity of carbonate of lime in the form of living 

 organisms in the surface waters to be 2-545 grammes, so that if 

 these animals were equally abundant in all depths down to 100 

 fathoms, it would give 16 tons of carbonate of lime to each square 

 mile of 100 fathoms depth.^ There is no reason, however, why 

 organisms contributory to sediment should not extend to, and 

 even become more abundant towards the bottom. In the absence of 

 knowledge as to the dm-ation of life in such minute marine organisms 

 as Globigerina, we are without data for estimating the rate of depo- 

 sition in deep seas. Although at great depths shells of Foramini- 

 fera are reduced to bicarbonate, this does not seem to result in loss 

 of material, for the samples of deep sea-bottom that have been 

 dredged, and our own Chalk formation, tend to show that the supply 

 of lime is not kept up to any extent by the dissolution of dead 

 organisms. 



The continuously increasing weight of sediment and of water 



1 Sir J. Herschel was of opinion that the weight of sediment displaced by the sea 

 produced elevation and depression along coast-lines (Phys. Geogr. p. 116). 



2 This would deposit, if replenished annually, one inch of sediment in 8,000 years. 

 If life extended equally to 2,000 fathoms, one inch would be produced in 400 years. 

 If 12 generations were produced per annum, one inch would result in 33 years, and 

 this might be more than doubled by the decay of life at the bottom. 



