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—a scarcely tenable hypothesis as applied to the mighty deep—or we must suppose with Carnall, as H. Hoefer has recently done, a subsequent redeposition of the primitive metallic salts contained in minute quantities in the sea-deposits—in other words, their solution and reprecipitation at certain horizons. Hoefer cites the lead and zinc deposits of Upper Silesia and other districts, which occur in marine Triassic limestones. He assumes the maintenance of uniform horizons by these deposits to be demonstrated, but points out that some of these horizons were already orebearing when first formed. In short, a number of investigators have adopted the hypothesis of an original ore-deposition from the ocean without giving any other reason than the observed relations of stratification. Yet, in a considerable experience with ore-deposits in marine limestones, genuine ore-beds are scarcely ever found among them, but always only ores of subsequent introduction ; so that we are warranted in believing that such ore-beds proper do not exist. As to the primitive ore contained in marine sediments and precipitates, innumerable chemical analyses, especially of limestone, have failed to show the metallic traces which, according to the above hypothesis, should be present. Ore-deposition in Fresh Water. —The demonstration of direct ore-deposition in fresh-water strata encounters the same difficulties, though it may be supported by the same chemical speculations. Here the hypothesis is favoured by the analogy of the lakes of regions without drainage to the sea, in which the salts brought in by rivers are necessarily concentrated by evaporation. But, since organic life is restricted in these salt lakes to a few animal species, the analogy can have but a limited application. Moreover, it would be necessary to suppose cataclysmic changes, like the interposition of a period of no drainage in the midst of an epoch of fresh-water sedimentation. Without the assumption of such cataclysms, we cannot believe that the Mannsfeld hwpfers chiefer, in which the organic (fish) remains can be traced continuously from foot- to hanging-wall, could, be explained in this way. It deserves mention that some of the earlier geologists, like Freiesleben, accepted the sometimes contorted attitudes of the palaoniscus in the kupferschiefer as a proof of contemporaneous ore-depositions, and alleged that these fishes had been thrown into violent contortions by the copper solution, in which condition they died, and were buried in the sediment. The naivete of this diagnosis, which, nevertheless, some modern writers have not hesitated to repeat, is evident. Contorted fish-remains occur in other formations outside of the kupferschiefer, and clearly show the advanced stage of decomposition in which the bodies reached the sediments. The Kupferschiefer of Mannsfeld. —The Mannsfeld kupferschiefer, as is well known, is a thin bed of bituminous slate, lying between the Permian sandstone below and the marine member of the same formation, the zechstein, above, and containing sulphides of copper, silver, lead, zinc, antimony, mercury, nickel, and cobalt. The copper amounts to 441b. to 661b., and the silver to 4oz. to soz. troy, per metric ton of 2,2041b. In polished sections, the ore can be seen in thin leaves lying between laminae of slate, and often accompanied by gypsum. But the same ores occur in scattered bunches in the sandstone below, and small bodies of redruthite are found in the limestone above. This circumstance alone, that ore occurs also in the marine limestone, above the freshwater kupferschiefer, is unfavourable to the contemporaneous origin of ore and rock. Kupferschiefer in Thuringia and Bohemia. —The same bituminous slate occurs in the Thuringian forest on the south slope of the Hartz, and at other points a considerable distance away. It must therefore have been deposited in a large basin. But it is a question whether it anywhere carries ore and deserves the name of kupferschiefer. In north-east Bohemia, the same Permian slate, with almost the same fossils, is widely distributed, but without the marine member which covers it in Germany. The Permian of Bohemia carries copper-ores in many places; and in one locality, namely, at Hermannseifen, these ores occur in the bituminous slate, which might properly here be called kupferschiefer. Precisely the same difficulty exists at Mannsfeld, and in the Thuringian forest, as Cotta reports in part as follows : " These conditions have influenced the ore-bearing character of the strata traversed by them. This influence is shown in the increase or diminution of the proportions of ore, not only in the immediate neighbourhood, but sometimes also for a considerable distance, even as far as the next master-fault. It is shown also in the transfer of the metallic contents from one stratum to another." This and other observations concerning the influence of the faults upon the ore-distribution bear decidedly against the contemporaneity of the ore-deposits, and in favour of a later introduction of ore through the fault-fissures. But this conclusion becomes much clearer upon a consideration of the remaining occurrences. Thus, according to Cotta, the kupferschiefer at the edge of the Thuringian forest is not so rich in ore as on the southern border of the Hartz. More important than the copper-slate itself are the fault-fissures which traverse the whole group of strata, but only carry ore in certain zones in which they intersect certain strata—the kupferschiefer among them. " Strange to say," observes Cotta, " near Camsdorf it is almost exclusively where the kupferschiefer has suffered such disturbances that it is rich enough to repay mining." In speaking of Eiegelsdorf he says, " The cobalt-ores have in some cases made their way from the veins into the country-rock." Westpihalia. —At Stadtberg, in Westphalia, there are even several copper-bearing strata, and these are cut by copper-bearing veins. At Bieber, veins traverse the whole group of strata into the underlying mica-slate, and " the irregularly distributed ore occurs, strange to say, chiefly interleaved in the mica-slate, and not, as in the Hartz and the Thuringian forest, in the horizon of the kupferschiefer; while, on the other hand, the impregnations from the veins have penetrated chiefly the bituminous marly slate." In consideration of the expressions partly quoted verbatim above, it is difficult to see how there can be any doubt of the secondary nature of the ore-deposits in the kupferschiefer throughout. Yet Groddeck has reproved me for coming to this conclusion. He says himself expressly