1891.] 
257 
[Whittle. 
the deep sea nodules are but the remains of these. Structurally, 
evidence of one or several neuclei about which the oxide formed 
in rude concentric layers still remains as areas of red or white 
clayey material — the residum resulting from decomposition. In 
many cases the nodules were undoubtedly organic and careful 
search will probably reveal fossils ; but the zone of manganese 
ore owing to its being a water way is a zone of decomposition and 
hydration. Where the strata underlying manganese-carrying 
rocks are sandstone or other pervous rocks concentration does 
not take place, the grade is poor, and the ore is apt to occur with 
large quantises of silica or silicates, as on the Pacific coast, and it 
is disseminated irregularly so that it is valueless as a marketable 
ore. The occurrence of melaphyre at the base of the limestone 
on Quaco Head is paralleled by most of the European deposits ; 
but is not common in this country. 
Genetically considered the history of our manganese depos- 
its along the Atlantic coasts seems to me essentially as follows, 
ignoring the processes which build manganese, iron, and phospho- 
rus into concretionary masses in the great depths of the ocean : 
Primarily, nearly all manganese occurring as beds must have been 
derived from the sea water, which is well known to carry an ap- 
preciable percentage of it as well as phosphorus and iron. Various 
dredging expeditions have noted the intimate association of man- 
ganese and phosphatic nodules with red, calcareous diatomaceous 
ooze of the deep sea principally along the 2600 fathoms sounding. 
— The similarity in appearance and chemical composition of these 
nodules with those of Quaco have already been pointed out. 
Going back in the history of this deposit we find it occupying a 
position comparable to the deeper portions of the ocean floor at 
present. Alternating strata of calcareous red ooze and limestone 
having manganese nodules lay on a massive base of malaphyre. 
These strata have been indurated and elevated, and the mangan- 
ese whicli occurred in these as disseminated grains and nodules 
has by a process of concentration wholly or partially re-concreted 
into u kidney ore” and stalactitic masses, the impervious charac- 
ter of the stratum below permitting and causing this concentra- 
tion to take place at or near the top of the impervious layer, as 
this would be a zone maximum interstitial water. Theoretically 
stalactites would be entirely reconcreted matter, the “kidney ore” 
wholly or partially, while the porous varieties would probably con- 
PROCEEDINGS B. S. N. H. 
VOL. XXV. 
17 
May 1891. 
