12 0. B. B0GGILD. BOTTOM DEPOSITS. [norw. pol. exp. 



sediments that are carried out into the sea, we may assume that the rapidity 

 with which the deposition takes place is about proportional to the amount of 

 brown in the colour of the sample. It is not impossible, however, that several 

 different factors, such as temperature, currents, etc., may modify the condi- 

 tions to some extent. The amount of lime it contains does not seem to 

 influence the colour of the clay in any way, except in giving it a lighter shade. 



With regard to the circumstance that in one part of the sea-bottom, 

 deposits may be found in which the upper and lower layers are of different 

 colours, it seems most natural to assume that it is due to changing rates of 

 sedimentation. It is also possible to imagine other reasons; for it appears 

 that on shaking a sample into a little water, the heavier parts are precipitated 

 first as a grey layer, and then above this the lighter, considerably browner 

 parts. We should imagine that this separation takes place when the sample 

 is taken, were not the apparatus constructed in such a manner as to make 

 this impossible; the bottom-deposits may possibly have been previously set 

 in motion by some large animal or other. The results of this would be that 

 the uppermost brown layer will be of a very fine, clayey consistency, while 

 the lower will be sandy clay. This is the case with several of the deposits 

 from the Indian Archipelago ' ; first there is a layer of brown clay of a pasty 

 consistency, wich attains a thickness of up to 15 cm., and below this there 

 is grey, green, or blue clay. This circumstance has not yet been very closely 

 investigated, however, and may possibly be due to other causes. 



In the North Atlantic nearest the coasts of Norway, there is according 

 to Schmelck, grey clay, and beyond this brown clay. The latter, nearest to 

 the grey clay's territory, forms as a rule only a thin layer above it, getting 

 thinner with a nearer approach to land. Here the brown clay is expressly 

 designated as sandy clay, and cannot be separated by movement in the clay. 

 The probability thus is, that formerly, at the time when the grey clay was 

 deposited in these localities, there has been considerably greater sedimentation. 

 It has not been decided whether this can be traced back to the Glacial Period, 

 or only to the last, more humid period. The latter is the more probable, as 

 it is scarcely possible to imagine that the deposition takes place so slowly 

 that only a very thin layer of clay has been formed since the Ice Age in a 





1 "Die niederliindische 'Siboga' Expedition, von Prof. Max Weber". Peterm. Mitt. 1900. 

 Heft VIII. 



