1868. | The Iron Ores of Great Britain. 37 
found to coat only those surfaces which face in a peculiar direction, is 
well worthy of attention in the study of these obscure phenomena.” 
Besides the Spathose ores of Weardale, we have the same ores 
occurring in great abundance on Exmoor, and they are worked 
extensively on the Brendon Hills, near Watchet, over a length 
of nine miles, to Eisen Hill. At Perranzabule, on the north coast 
of Cornwall, a still more remarkable deposit of these ores exists, but 
at the present time they are but slightly worked. In the northern 
corner of Perran Bay a lode appears in the cliff, with a width of 
nearly 100 feet, and it has been traced for some miles inland and 
worked at several pots. Beyond this brief notice, space cannot 
be given to the further consideration of these most interesting Iron 
ores. 
The Argillaceous Iron Ores of the Lias.—The Cleveland Iron 
ore is the finest example we have of this class of ore. The immense 
extent of this deposit, the value of the Iron works which have 
arisen amidst the Cleveland Hills, places this district amongst the 
first of our Iron-producing districts. 
This remarkable deposit may be traced by its outcrop for miles 
along the escarpments of the Cleveland Hills. Above the flat land 
which extends from Redcar to Middlesborough there crops out a 
solid stratum, often fifteen feet in thickness, of this Lron-stone. It 
is a deposit of a green or grey colour, having generally an oolitic 
structure, and containing numerous well-known fossils of the 
Marlstone, especially Belemnites and Pecten Aiquivalis. The plan 
and section, Figs. 7 and 8, will show the mode of occurrence of this 
ore. This vast ferruginous deposit is composed, to a great extent, 
of Carbonate of Protoxide of Iron. We know that such a deposit 
could not be formed, unlcss it was precipitated from water charged 
with Carbonic acid in excess. We have no evidence that such 
conditions ever prevailed, to the required extent, over this district, 
when those Iron-stone beds were being formed. Mr. Sorby has 
drawn attention to the fact that if the Iron-stone be examined it 
will be seen that it contains, more or less, entire portions of shells. 
All the indications appear to show that the Cleveland Iron ore was 
deposited probably as a limestone, containing a large amount of the 
oxides of Iron and organic matter. By their mutual reaction these 
would give rise to the bicarbonate of Iron, which in solution, per- 
colating through the limestone, would remove a large part of the 
carbonate of lime and leave in its place carbonate of Iron. 
It is our object in writing this paper, to draw more especial 
attention than has hitherto been done to the Heematites, and the 
Argillaceous Carbonates of the coal-measures, as related to each 
other, in their mode of formation. 
It will be evident to everyone who carefully studies the conditions 
of the clay band Iron-stones spread out in beds amongst the seams 
