474 



MR J. Y. BUCHANAN, F.R.S., ON THE 



111 connection with these Tables it may not be amiss to quote the analyses which I 

 made of some nodules in 1876, and published in the Proceedings of this Society.* The 

 samples analysed were from four different localities, two of which are identical with those 

 from which the nodules I.-V. came. 



Nos. 2, 4, and 5 were from the same place, No. 2 being the matter collected round a 

 shark's tooth as nucleus, Nos. 4 and 5 being the outside rinds of ordinary nodules. 



The results are given in the following Table, the numbers being in many cases the 

 means of several observations : — 



Locality. 





A 



B 



C 



D 



E 



F 



G 







No. 



Insoluble 

 Residue. 



O 



Mn0 2 



MnO 



Fe 2 3 



A1A 



H 2 



Na 2 



Lat. 



Long. 



13° 52' S. 



149° 17' W. 



2 

 4 



17-55 

 15-30 



6-13 



5-92 



33-30 

 32-23 



27-18 



23-86 













5 



15-30 



6-49 



35-28 





24-85 





10-2 





37° 52' N. 



160° 17' W. 



6 



36-24 



6-49 



24-41 





20-16 



3-83 



7-70 



5-98 



42° 42' S. 



134° 10' E. 



7 



17-98 



7-54 



41-11 



33-53 



18-04 



2-55 



7-31 





22° 21' S. 



150° 17' W. 



8 



21-74 



5-19 



28-20 





24-52 



7-67 



8-54 



8-5 



A is the residue which remains undissolved after treating the mineral with strong- 

 hydrochloric acid, evaporating to dryness and redissolving. In No. 5 it contains 5 5 "16 

 per cent, silica, and in No. 6, 82*27 per cent. 



B is the available oxygen determined by Bunsen's method. 



C is the Mn0 2 equivalent to the available oxygen. 



D is the MnO found by weighing as Mn 3 4 . 



E is the Fe 2 3 found by titration with SnCl 2 . 



F is the alumina found by subtracting the Fe 2 3 found in E from the weight of the 

 precipitate with acetate of soda. 



G is the water expelled on ignition ; it is obtained by deducting two-thirds of the 

 oxygen found in B from the loss of weight by ignition. 



The samples were dried for ten or twelve hours at 140° C, and therefore the 

 percentages are higher than those in Table IV., the samples in it having been analysed 

 air-dried. 



From these Tables it will be seen that nodules from all localities have similar composi- 

 tion. The most important difference between the littoral and the oceanic nodules is, that 

 in the former the manganese is less highly oxidised than in the latter. In the oceanic 

 nodules, when we consider the manganese alone, the peroxide is very little short of Mn0 2 ; 

 in the littoral ones it is very little over Mn 2 3 . In both oceanic and littoral ones the 

 manganese is more highly oxidised in the kernels than in the rinds ; this difference is par- 

 ticularly marked in the littoral ones. Nickel, cobalt, and copper are probably present in 



* Proc. Roy. Soc. Edm., 1876, vol. ix. p. 287. 



