34 The Iron Ores of Great Britain. [Jan., 
ceous iron. In the Whitehaven district the ore is found filling 
cavernous spaces, which had evidently been formed in the limestone 
previously to the deposit of the Iron; these caverns being probably 
due to the action of water charged with carbonic acid, which readily 
dissolved a certain proportion of the limestone. In the Low Furness 
district, at Rickett, Hills, and Mousell, the Hematite is found in 
lake-hke deposits, which have been well described as “dish-shaped.” 
These dishes of ore run from fifty to sixty yards in width, and are 
usually from eighteen to twenty feet deep. At Roanhead the ore 
is found in two basins, which are slightly connected with each other, 
but they have nothing of the character of a mineral lode. These 
basins are covered generally with sea-sand, which is often overlaid 
with a tenaceous clay. Nothing like a mineral lode occurs either 
at Whitehaven or at Ulverstone. At Stainton, a chasm worked 
open to day was long looked upon as a vein of ore, but the full 
exploration of it proved the contrary. Fig. 4 is a section of this 
chasm, which was worked altogether to the depth of sixty yards. 
The stone arch shown was built to support the walls of the fissure, 
it being thought that the ore would be found to a considerable depth 
below. Within a short distance a bed of clay, locally called “ blue 
hunger,” came in, below which there was not a trace of Iron ore. 
Brown Hematite-—The Forest of Dean may be regarded as 
the chief locality for this variety of Iron ore, about 150,000 tons 
being raised annually. The Forest of Dean ores are commercially 
classified into Brush Ore, containing 90 per cent. of Sesquioxide of 
Tron; Snuth Mine giving 89 per cent., and Clod or Grey Vein 
about 50 per cent. These iron ores occur under much the same 
circumstances as the Red Hematites of Whitehaven. The iron- 
stone formation is immediately overlaid by the ‘‘ Whitehead Lime- 
stone,” a regularly stratified rock, the beds of which are often 
highly crystalline. This limestone is locally called “ crease,” and is 
traversed by innumerable small joints, which appear to have arisen 
from a shrinking, probably during the consolidation of the mass. 
The worked-out spaces in the “ Mine Measures,” that is,—the iron- 
stone beds which have an average thickness of twenty-five yards,— 
are so extensive that they have been compared to the crypt of a 
cathedral. These prove the deposit to have taken place in caverns 
which had been previously formed by the removal of the limestone. 
There are many curious phenomena connected with the Iron ore 
formations of the Forest of Dean, which demand a careful examin- 
ation. It is not, however, possible in this place to give the required 
consideration to those, since the space which can be allowed to this 
article is fully occupied, with the general review of our iron-stone 
deposits, and remarks on the conditions under which they appear 
to have been formed. 
Some valuable deposits have been recently worked in Gla- 
