528 Mr. J. Murray on Oceanic Deposits examined 



Atlantic. 



fms. 



fins. 



fms. 



fms. 



fms. 



2740 



2385 



2700 



2650 



2700 



2950 



2675 



2600 



2500 



2750 



2750 



3000 



2475 



2360 



2700 



2800 



2975 



2600 



2575 



2350 



3150 



3025 



2850 



2850 



2275 



2720 



2800 



2675 



2875 



2550 



2575 



2960 



2800 



2750 



2650 



2435 



2850 



2650 



2750 







Southern and Pacific 



Oceans. 





fms. 



fms. 



fms. 



fms. 



fms. 



2600 



2450 



2575 



3125 



2325 



2600 



2325 



2800 



2025 



2385 



2600 



2300 



2900 



2850 



2450 



2900 



2475 



2775 



2950 



2375 



2650 



2450 



2050 



2875 



2250 



2325 



2500 



2530 



2775 



2335 



2450 



2425 



2900 



2225 



2270 



2440 



3900 



2300 



3000 



2400 



2275 



3600 



2350 



2900 



2600 



2550 



2900 



2900 



2610 



2550 



2650 



2300 



2740 



2350 



2300 



The Manganese in Deposits. 



The peroxide of manganese, in the form of minute grains, concretions, 

 nodules, aggregations, or incrustations, occurs widely distributed in 

 ocean-deposits. It has been met with most frequently in the deep-sea 

 clays ; indeed it seems to be present in all of them, sparingly in some 

 localities, abundantly in others. 



It is, however, not confined to these clays ; it has been found in most 

 of the other deposits and at all depths greater than 500 fathoms. In 

 the Globigerina- and Radiolarian ooze and in the clays it usually 

 assumes the forms of minute grains, pellets, and nodules. In those 

 bottoms to which it gives a chocolate-colour, the higher powers of 

 the microscope show small, round, red-brown grains of mauganese, often 

 with a dark spot in the centre. 



The nodules vary from little pellets to masses of a large size and o£ 

 several pounds in weight. In some regions every thing at the bottom, 

 even the bottom itself, would appear to be overlaid by and impregnated 

 with this substance. In the foregoing list, as at No. 318 and elsewhere, 

 some of the nodules have been described with a little detail. The varie- 

 ties which are most commonly procured may be here mentioned : — 



Nodules of a black-brown colour throughout, the manganese being 

 laid down in concentric layers, which are evident from their 

 enclosing; lines of red clay. 



Nodules having a nucleus of pumice which is surrounded by concen- 



