118 
The general appearance of the section shows that the 
contortions of the series have been produced by a slip, most 
probably at the time when the Red Rock Fault was formed. 
This is evident not only from the disturbed beds lying 
between two series, which have been very little bent, but 
a]so from the peculiar appearance of the layer of shale 
beneath, and the confused mass of broken sandstone above. 
In the underlying shale there are two or three very thin 
seams of carbonaceous matter, which are rendered rather 
conspicuous by their dark colour ; these are curiously con- 
torted, having been completely twisted in no less than four 
places, the interior of the folds being occupied by confused 
masses of variously coloured crushed shale. 
III . — Occurrence and Properties of the MnCh. 
The most typical specimens of oxide of manganese (wad) 
are to be obtained from the fissures in the lower bed of 
sandstone in the section just described. Here it occurs in 
considerable quantity, and is in a very accessible place. 
The walls of the cavities produced by the fissuring of the 
rock are covered with a layer of the mineral, never more 
than \ inch in thickness, which is not at all smooth on the 
exterior, but has the appearance of soot adhering to the side 
of a chimney ; this form is caused by a pellet -like structure 
assumed by the substance. The layer appears to cover all 
the walls of the cavities equally, not becoming perceptibly 
thicker on the lower sides, and not altering in appearance 
in different parts. 
But the most peculiar and characteristic feature of the 
wad in this sandstone is its occurrence in miniature columns, 
joining the two opposite walls of the cavities, and in long 
slender threads, stretching in all directions over the rough 
surface of the mineral-incrustation. So far as I have been 
able to ascertain, none of these columns or threads are 
perfectly solid but are all pierced longitudinally by a canal, 
which is often situated not quite in the centre; in some 
