COMPOSITION OF OCEANIC AND LITTORAL MANGANESE NODULES. 



475 



all, but their relative proportions are different in the littoral and in the oceanic nodules. 

 Cobalt can be determined in both, and ranges from 0'02 per cent, in Loch Fyne nodule 

 M to 0'34 per cent, in oceanic nodule V. Nickel is present in large though variable 

 quantity in the oceanic nodules, as much as 1*46 per cent, of oxide in II., falling to 

 0'47 per cent, in V. In the Loch Fyne nodules the presence of nickel was doubtful. 

 Copper was present in both classes of nodule. In the oceanic ones, however, the traces 

 were not always very distinct, whilst in the Loch Fyne ones they were very pronounced. 

 In testing for thallium, it was sufficient with oceanic nodules to moisten a piece of the 

 size of a bean with HC1 and place it in a platinum triangle over a Bunsen burner to get 

 a strong thallium line in the spectroscope. Thallium could not be detected in this way 

 in the Loch Fyne nodules. 



The insoluble residues were always tested quantitatively, and consisted, besides silica, 

 of alumina and ferric oxide, with smaller quantities of lime and magnesia. The silica, 

 however, of the Loch Fyne nodules was largely quartz, which was not the case with the 

 oceanic nodules. The percentage of insoluble residue varies much in both sorts, but it is 

 always greater in the Loch Fyne ones than in the oceanic ones. The percentage of silica 

 in the Loch Fyne nodules varies very little from 25, leaving from 2 to 6 per cent, of 

 bases in the insoluble residue. In the oceanic nodules, excepting IV., the silica varies 

 between 14*68 and 17"46 per cent., leaving from 2 to 3 per cent, bases in the 

 residue. In IV. the amount would be 44?. In the kernels (K) the moisture driven off at 

 100°, the carbonic acid, and the Fe 2 3 + Al 2 3 were determined, and we have the 

 following tabulated summary : — 



Sample K — Kernels of Loch Fyne Nodules. 



Moisture at 100" 



8-23 „ 



Available oxygen, 



6-26 



MnO, . 



. 3715 



Fe 2 3 +Al 2 3 , . 



4-78 „ 



CuO, . 



trace 



NiO, . 



doubtful trace 



The insoluble residue was not determined. 



In order to obtain some knowledge of the other constituents of the Loch Fyne 

 nodules, a number of nodules were pounded up and mixed, so as to form an average 

 sample in which the determinations were to be made. They contained a certain amount 

 of soluble matter from the sea water, and, if it had been intended at first to make a 

 complete analysis, the whole of this sample would have been extracted at once. This 

 was not done, and the various portions, X, Y, and Z, have been treated separately. 

 Particulars follow. 



VOL. XXXVI. PART II. (NO. 17). 4 B 



