134 
(Mn, O,) in the ashes of the Sweet Flag, Acorus calamus ; and 
Frescenius eleven per cent. in the ashes of the Beech, Fagus 
sylvatica. 
We do not always find it in the ashes of these plants, but 
they appear to have the power of appropriating it when it happens 
to be in their vicinity. 
The Manganese to which I specially refer I found in an 
irregular layer in the gravel under Bigberry Wood, near Canter- 
bury, at about 12 feet from the surface, and 200 feet above sea 
level. From its dark colorI at first thought it was some form of 
organic matter, or iron reduced to the protoxide by vegetable 
matter. The latter is probably the key which unlocks to us the 
meaning, and shows the cause of its occurrence. The vegetation, 
living and dying on the marshy flats and in the shallow pools, 
gives off vegetable acids as well as carbonic acid. 
These acids dissolve the iron and manganese contained in the 
surrounding beds, the organic matter having previously reduced 
them to a condition of lower oxide, and on becoming once more 
oxidised are again precipitated as the Red oxide of Iron and Black 
oxide of Manganese. 
Manganese occurs sometimes in very unexpected places. The 
dredging operations of the Challenger expedition carried on in the 
abysmal depths of the ocean, brought up nodules of Manganese from 
twelve thousand feet. These were associated with calcareous 
Foraminifera and siliceous Radiolaria, mixed with an exceedingly 
fine clay, coloured red by oxide of iron, and sometimes of a choco- 
late tint from manganese oxide. 
Dr. Geikie says, that this deposit, covering the floor of the 
ocean in its greatest depths, is one of the most singular features of 
recent discovery. It sometimes incrusts bits of pumice, bones, &c. 
The nodules possess a concentric arrangement not unlike those of 
calculi. That they are formed on the spot, and not drifted from a 
distance, is clear from their containing abysmal organisms, and 
enclosing more or less of the surrounding bottom, whatever its 
nature may happen to be. Mr. Buchanan has recently found 
similar manganese concretions in some of the deeper parts of 
Loch Fyne. 
In the slates now worked in a quarry above Beltws-y-Coed, in 
North Wales, I found cavities filled with a soft earthy brown 
mineral containing a large quantity of Manganese; this had 
probably the same submarine origin as the nodules found by deep 
sea dredging. 
These facts give us an enlarged interest in connection with the 
