NOTES ON THE GEOLOGY OF CLEVELAND. 



91 



metal too, it appears — the seam assumes such an aspect as might 

 deceive many ; since owing to the percolation of water through the 

 countless cracks and fissures at its outbreak, the iron has become 

 oxidised gradually more and more ; and where not quite oxidised 

 throughout, the blocks consist of a nodule in the middle, of almost 

 unaltered dark blue ore, of nearly equal parts of protoxide of iron 

 (about thirty-three per centum where richest), and peroxide of iron 

 (about thirty-two per cent.), and several concentric layers of brown 

 ore, the outer of which contains all the iron in a peroxide state, and 

 clearly showing a change to have taken place from a protoxide to a 

 hydrated peroxide. In the drift made a little eastward of the quarry 

 we find, after eighty yards of hard shale, other eighty yards of the 

 altered brown ironstone, with blue nodules, which increase in size as 

 we proceed, until at last we reach the solid rock, unaltered by any 

 percolation ; intensely hard ; of a blackish-blue colour ; highly mag- 

 netic ; lying in horizontal layers ; scarcely fissured, and thirty-two feet 

 in thickness. A considerable distance from this drift it has been 

 twice bored down to, at a depth of forty -five fathoms, and proved still 

 of the same great thickness : although its per centage will probably 

 average less than has been given above, there seems no reason to 

 fear that the seam will soon be exhausted. Some have thought that 

 this rock exhibited symptoms of igneous origin ; others have made it 

 out to be affected by heat, subsequently to its deposition ; and some 

 have even tried to trace a cause-and-effect — a connection between the 

 Whin- dyke, seven miles away, and this astonishing stratum of iron- 

 ore. There is however not the slightest foundation for any such 

 surmises, as we find it in a horizontal position, in distinct lamina?, 

 between the upper Lias and sandstone-rock of the Inferior Oolite, — 

 most assuredly the natural place of its deposition. The depositing 

 waters were greatly impregnated with oxide of iron, which congre- 

 gated round any solid object ; and accordingly in each oolitic particle, 

 there is some nucleus of shell, sand, &c, which is perceptible under 

 the microscope, as in oolitic limestones, in the interior of each of the 

 grains. There have, I believe, been no organic remains discovered in 

 the rock, owing, it is possible, to part of the iron being in the peroxide 

 state — in which case it is a noticeable fact that there is either very 

 great scarcity, or an utter absence of traces of animal life. Whether, 

 however, these two facts, so generally coincident, are related as cause 

 and effect, is a question for further consideration. The Lias iron-seams, 

 which contain the iron in a protoxide state only, show the ocean at 

 the period of their deposition to have been very prolific in organic 

 life. 



An interesting view of this oolitic iron-seam may be obtained by 

 tracing its development from Orunkley Grhyl up the eastern side of 

 Great Eryup Dale to Fryup Head, and again to its appearance in 

 Northdale, on the other side of the moor, and opposite to the great 

 iron-quarry of Rosedale, which I have just remarked upon, and 

 where, as I observed, the seam appears to attain its maximum thick- 

 ness and to possess also its maximum dose of iron. The outbreak of 



