OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 67? 



" It is a very interesting mixture of Arctic, special Antarctic, and subtropical species. 

 There are also some others difficult to determine with certainty from the preparations 

 I have made so far, but I hope to be able to give you a final report soon. 



"(Signed) H. H. Gran." 



Terrigenous Deposits, particularly Glacial Muds and Clays. 



The greater number of the deposits collected by the Scotia, including practically all 

 those obtained in the Weddell Sea south of the 60th parallel, are of terrigenous origin, 

 of the type which I propose to designate as glacial mud or clay. This is composed almost 

 entirely of material derived from Antarctic lands and distributed in the surrounding seas 

 partly in suspension in the water, partly through the medium of floating ice, especially 

 icebergs. In the Challenger report and map this deposit is not distinguished from 

 other Blue muds of terrigenous origin, and in my preliminary report on the deposits 

 obtained by the Scotia, published in the Scot. Geog. Mag., 1905, I also included it 

 amongst the Blue muds, pointing out, however, some respects in which it differed from 

 those surrounding non-glaciated lands, and, in particular, distinguishing certain samples 

 as approaching Red clays in some of their characteristics, although differing markedly 

 in others. Philippi, in his report un the deposits obtained by the Gauss, first proposed 

 the separation of this deposit from terrigenous deposits under the title " Glacialmarine- 

 ablagerung," basing his classification on the following main differences : — 



(1) Almost complete absence of CaCOg from the deposits. 



(2) Small amount of organic constituents. 



(3) Very unequal size of the mineral particles, especially of the coarser components. 



(4) Character of the " fine washings " — these consist for the most part of exceedingly 

 fine "rock flour," whereas in the Blue muds proper they consist chiefly of amorphous 

 clayey material. 



He says further that this marine glacial deposit consists essentially of a mixture of 

 the finest ooze with sandy and gravelly constituents with, here and there, large 

 fragments and stones. According to the size of the fragments and the preponderance 

 of one or other component, one may get an oozy or muddy sand or gravel, or an ooze 

 with sandy or gravelly constituents. 



The deposit is in general the finer grained the farther it is from the ice edge and 

 the deeper the water ; only exceptionally within the pack-ice zone does it contain any 

 lime and is usually free from diatom frustules — facts all the more striking seeing that 

 the surface waters contain numerous Globigerinidae and diatoms in enormous numbers. 



With this description I am, from my examination of the -Scotia deposits, in 

 substantial agreement. Some of these deposits are most aptly described as muds, but 

 many are unctuous tough clays requiring much rubbing to break them down in water. 

 In ordinary parlance they would undoubtedly be described as " clays," and although 

 microscopic examination reveals the fact that the finest constituents do consist for the 



TRANS. ROY. SOC. EDIN., VOL. XLIX. PART III. (NO. 10). 90 



