TRANSACTIONS OF SECTION C. 533 



category ; that, in sliort, he saw no reason to doubt that the era of the canoe was 

 prior to that of Betida nana in Devonshire ; prior, also, to the accumulation of the 

 Head ; and that, if the Head be of Glacial age, the canoe belonged to at least 

 Glacial times. 



2. On the Origin of the Hannatite Deposits in the Carboniferous Limestone. 

 By Edwakd Wethered, F.Q.S., F.G.S. 



The author contended that the so-called 'pockets' of haematite which occur in 

 the Carboniferous Limestone were caverns and fissures into which the ore had been 

 introduced by water agency. There were two or three signs which indicated an 

 approach to a pocket of ore. 



1 . Joints appeared in the rock through which water percolated. 



2. An ordinary cavern opened out, termed by the AVelsh miners a ' locus,' the 

 sides of which were coated with large crystals of carbonate of lime. 



3. Traces of iron are found in the * locus.' 



The fact that the first indications of ore were cracks in the rock, down which 

 water percolated, certainly pointed to tlie inference that by a similar percolation, the 

 haematite has been brought into its present position. That it has been de- 

 posited by aqueous agency was clear from the crystalline character of some of the 

 ore. Further, there was just what would be expected from water containing the 

 carbonates of lime and iron in solution wliere not exposed to the atmosphere, namely, 

 lime has been first deposited and subsequently h}'drated peroxide of iron. 



The next point considered was, from whence was the iron derived. The highly 

 ferruginous character of the Carboniferous strata was well understood, and the fire- 

 clays indicated that large quantities of iron had been rendered soluble by the de- 

 oxidizing influence of decaying vegetable matter, and removed by the percolation 

 of water. But, as to whether it was this iron which had given rise to the Carboni- 

 ferous Limestone hiematite deposits was a matter for consideration. It was doubt- 

 ful whether there would have been sutticient time for the fissures and caverns to 

 have so far developed as to form receptacles for the coal-measure water charged 

 with carbonate of iron. It must, however, be remembered that after the uplifting 

 of the Palaeozoic rocks there was a vast lapse of time during the denudation by 

 the Triassic Sea, and that much of the limestone, not now overlain by the Goal 

 Measures and jMillstone-grit, was covered by those beds for a considerable time. 

 Further, water percolating through the Coal Measures would become highly charged 

 with carbonic acid, given ort" from vegetation undergoing transition into coal, and 

 water, so charged, would not be so long in dissolving and eroding out caverns. 



Mr. Etberidge had referred ^ the origin of the Carboniferous haematites, in the 

 West of England, to the infilling of faults, fissures, etc., during the denudation by the 

 Triassic Sea ; but stated that " doubtless the percolation of water through overlying 

 strata, highly charged with oxides of iron, had been a source and mode of accumu- 

 lation." Though the author was disposed to consider it possible that some of 

 the hrematite may have been derived from the percolation of water through 

 the C'oal Pleasures and Millstone-grit, yet he agi-eed with Mr. Etberidge 

 that the most probable source was from the Trias rocks; not, however, during 

 the accumulation of the strata composing that formation, but by subsequent 

 percolation of water after consolidation of the beds. This water, on arriving at the 

 Carboniferous Limestone, would flow down the cracks, fissures, and joints, provided 

 there were such, but a comparatively small portion would filter through the actual 

 rock on account of its being but slightly pervious to water. The author considered 

 that it was owing to this fact that we generally find haematite where the Magnesian 

 Conglomerate rests upon the ( 'arboniferous Limestone. The water being unable to 

 penetrate the rock, would naturally find an outlet at the junction of the two forma- 

 tions, and the conditions would soon be arrived at when the deposition of the iron 

 would take place. 



' Quai't. Journ. Gcol. Society, 1870, ix. 1S5. 



