41 



order, pnd how induced; a. tas^': made difficult by the low concen- 

 tration8 of the solutions with which it is necessary to deal. 



It is not necessary to mention here the multiplicity of problems 

 of this sort. Chemical' problerr.e equally fundamental are inhert5nt 

 in present-day study of the sea floor, for the geo-physicist^ is 

 directlv concerned with the wl'ole c;aa:ut of reactions that talce place 

 in the abyssal depths of the sea, it being an open question whether 

 many of those that have been proposed (although doubtless falling 

 within the range of potentialities) are actually of the importance 

 that have baer. accredited to ther/'. on theoretic grounds. With regard 

 to the sea bottom, as well as with regard to the water itself, first 

 rank might be given to the problems of lime chemistry, with ramifica- 

 tions too complex for discussion in this report. The chemical as- 

 pects of the precipitation of calciiom carbonate in tropical waters 

 are now being taken up afresh. If this precipitation be chiefly 

 mechanical, as now seems likely (Page j.l ) , we need to learn which 

 of the various reactions that have been suggested as the potentiel 

 causes are actually operative on a large scale in the sea. The re- 

 actions that accomiDEiny the formation of phosphatic concretions and 

 of glauconite on the bottom also need further examination, while the 

 proble:n of the chemistry of the deposition of iron in the sea floor 

 is a major one and to date practically untouched (Page 7 ). 



So, too, the chemistry of the natural distillation of organic 

 materials in the bottom muds that are/ now believed by many to have 

 been responsible for the formation of petroleum and other hydro- 

 carbons. 



We have still to learn the chemical character of the water that 

 is entraioped within the sediments, a very important question because 

 the alterations that take place there in the solid materials depend 

 upon its alkalinity, carbon dioxide content, etc., of this water. 

 We think especially of the re- solution of lime there and in the 

 abyssal waters generally. Some such process has been widely postula- 

 ted to account for the fact that there is a limit to the depths down 

 to which lime sediments chiefly accumula-Ge, and it may explain the 

 fact thp.t the percentage of lime usually decreases in the oceanic 

 sediments from the uppermost layer downwards for we have almost no 

 empiric knoivledge as to the actual details of the solution which 

 proceeds at great depthsl The problems of lime solution introduce 

 the basic question of the efficiency of sea water as a solvent, not 

 only for lime, but for silica, for the various volcanic substances 

 that accumulate on the sea floor. Solution of a wide variety of 

 mdnerals is also constantly taking place all around the shores of 

 the continents, in combination v^dth the processes of mechanical 

 erosion by the waves and currents. And while this solution is slow, 

 it is not only unceasing now but has been unceasing for past geologic 

 ages. In short the total amount of material dissolved in this way 

 has been enormous. Fu.rthermore, some recent observations with regard 

 to the concentration of silicates in the water suggest that solution 

 of even these refractory materials may take place ra,pidly enough to 

 produce regional differences in the amo^-int of silicates in the v.^ater, 

 according as different sectors ci the coast contribute more or less 

 to the sea. It is also certain that the last ?/ord has not ye': teen 

 said as to the solution of lime from coral formations in tropical 

 waters, or from the accumulations of precipitated calci'om there. 



