121 
tint on exposure : its hardness is less than 1. It is easily 
crushed into powder between the fingers, and has a 
characteristic crispness. When heated in a closed tube 
water is evolved, and under the blowpipe it is infusible. 
Its streak is of a dark yellowish -brown colour. 
A quantitative analysis of the mineral gave the following 
as its percentage composition : — 
Mn0 2 = 33-634 
Fe 2 0 3 = 9-375 
A1 2 0 3 = 22-913 
Si0 2 = 16*815 
Water = 17-237 
99-974 
This analysis probably does not show the exact composition 
of the pure mineral, since it is almost impossible to obtain 
a sufficient quantity entirely free from the surrounding 
argillaceous matter. 
IY . — Distribution of Mn0 2 in Ratcliffe Wood. 
So far as I am yet aware, there is only one other spot in 
Ratcliffe Wood where oxide of manganese is to be seen 
occurring in the same form as the mineral in the section 
previously described. This is a few hundred yards to the 
east of the latter, and the deposit exhibits not only the same 
peculiarities but others which render it even more in- 
teresting. Here, as in the previously mentioned case, the 
mineral occurs both as an incrustation and pseudomorphic 
after rootlets ; but it is also in many parts covered with a 
thin layer of a white, translucent, crystalline mineral — a 
highly hydrated phosphate of alumina with a proportion of 
silicate — which, besides, mineralizes rootlets in an analogous 
manner to the oxide of manganese. 
In this same section, too, there is exposed a lenticular 
mass, 4ft. 6in. long and Sin. in greatest thickness, which 
is black, earthy, and moist, and evolves chlorine on treat- 
