S. R. Pattison — On the Pyrites Deposits of Spain. 59 



EXPLANATION OF PLATE IL 



Fig. 1. — FalcBopteris Hibernica, Sch. Restored, one-sixth the natural size. 2. 

 A pinnule, somewhat magnified, to show the venation and slight serration of 

 the margin. — 3. Fertile pinna, nat. size. — 4. Two cup-shaped involucres 

 attached to the filiform costa, greatly magnified. 



Fig. 5. — Sporangia of a Hymenophyllaceous.fern from the Coal-measures at Old- 

 ham. — 6. Sporangia of Hymenophyllum Tunbridgense^ Sm. — 7. Sporangium of 

 Folypodium vulgar e, Linn. — Figs. 5, 6, and 7 are magnified to the same ex- 

 tent. 



Fig. 8. — Transverse section of Osmundites Bowkeri, Carr. From the Lower Eocene 

 of Heme Bay. — 9. Two cells of this fossil showing the starch granules and 

 mycelium of a fungus still preserved. 



IL — Note on the Ptbitbs Deposits in the Pkovince of Huklva 



IN Spain. 

 By S. R. Pattison, F.G.S. 



("With a page woodcut.) 



THE method now adopted of working the lenticular deposits of 

 pyrites occurring in the province of Huelva by open cutting 

 and quarrying, is favourable to the examination of these singular 

 masses of mineral. The latter run parallel with the strike of the beds ; 

 they are generally, but not always, in close proximity to greenstone, the 

 greenstone often forming one wall or sahlband; they usually, but 

 not always, decrease in width as they go down, and sometimes end 

 in a boat form ; they are generally, but not always, marked by oxida- 

 tion on the surface, and generally, but not always, by a depression 

 between the two walls. The latter phenomena have been supposed 

 to have been occasioned by the ancient mining for copper having 

 worked away the upper surfaces and exposed fragments of mineral 

 to oxidation ; but the facts appear to be at variance with the causes 

 thus assigned, inasmuch as there is extensive colouration where there 

 have been no workings ; and on the other hand, no subsidence in 

 many cases where ancient workings exist 



A recent visit to the Buitron mine enables me to o£Fer a few 

 remarks on these deposits. The mass at Buitron occurs in a series 

 of thin-bedded coarse schists, with intercalations of greenstone, the 

 latter ranging with the beds, but occasionally bulging. The mineral 

 does not reach the surface. It appears as though it had been de- 

 nuded, and had yielded to the denuding force more freely than the 

 sides, which, however, are generally formed of bleached felspathic 

 clay-slate. The skeleton of the mineral mass is a fine siliceous sand, 

 permeated in various proportions with copper, averaging 3 per cent., 

 sulphur, pretty constant at 48 per cent. ; and about two shillings 

 worth per ton of gold and silver. Is it not possible that the metals 

 were introduced subsequently to the strata becoming vertical, by 

 sublimation, the chemical action having displaced one substance and 

 deposited another with the silex ? There is a kind of grain in the mass 

 of mineral similar to that of any interbedded grit. The overburden, 

 consisting of decomposed "country " reddened by oxide, is only a 

 portion of the adjacent surface rocks, deposited with, if not by, 

 water, in a hollow formed by denudation. The rubble over the mineral 



