xiv Contents 



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Ad vantages of the Millar-Casella thermometer . 45 



Water collected from intermediate depths with the 

 double stop-cock water-bottle during the whole 

 voyage without any loss of material .... 46 



Details of material lost . . . . . . 47 



Comparison of extreme depths at which hemp and 

 wire can be used respectively ..... 48 



Prevalent misunderstanding with regard to the rela- 

 tive rapidity of sounding and dredging with hemp and 

 wire respectively ........ 49 



Discovery of oceanic shoals in the " Dacia" by close 

 sounding with wire ....... 50 



The work of submarine cable engineers in repairing 

 jobs is often fruitful in furnishing data of the nature of 

 the bottom of the ocean and of the motion of its waters 51 



The author's work on the oceanic shoals discovered 

 in the "Dacia" in 1883 filled the lacuna in Murray's 

 theory of Coral Islands 52 



He postulated the shoaling of the deep water by the 

 aggregation of sediment until it reached so near the 

 surface as to be fit for the settlement of reef-building 

 corals on it. But the shoaling of the water by obstruct- 

 ing the all-pervading tidal wave, converts it pro tanto 

 into a tidal current, the effect of which, in deep water, 

 is to set a limit to the increase of a shoal formed of 

 sediment 53 



In the " Dacia" a shoal which was called the " Coral 

 patch" was shown to rise as a solid perpendicular pillar 

 from a shoal of sediment in 1000 fathoms to within 

 450 fathoms of the surface and formed of deep-sea 

 corals and other calcareous organisms . . . . 54 



It was in active growth and when it would reach 

 near the surface, if the temperature were suitable, it 

 would be colonized by reef-building corals. There is 

 little doubt that this intermediate pillar of cold-water 

 calcareous organisms is the immediate foundation of 

 oceanic coral islands ....... 55 



In the "Buccaneer" important work was done for 

 the first time in the detailed survey of the slopes from 

 the continental shores to the oceanic abysses and very 

 remarkable results were obtained .... 56 



Routine of the chemical work in the "Challenger" 

 Laboratory. Determination of the carbonic acid in sea- 

 water 57 



