399 



which, so far as this evidence goes, may have been deposited when the 

 rock was formed, or at any subsequent period. 



In a paper hj Mr. J. P. O'Reilly and myself, read to the Academy, 

 November 11th, 1861*, and in a subsequent memoir on the geology and 

 mineralogy of the Province of Santander, in the north of Spain, which 

 we published in the " Atlantis" f, and afterwards as a separate work+, 

 we gave an account of a remarkable fissure in the limestone in the 

 Valley of Udias, filled with hydrocarbonate of zinc, in which were im- 

 bedded numerous mammalian bones, and also teeth probably of Elephas 

 Primigenius. These fossils fix the relative age of all the great deposits 

 of hydrocarbonate of zinc in the Province of Santander. This is, there- 

 fore, the first instance in which the geological age of any ore has been 

 determined with certainty. The hydrocarbonate of zinc and carbonate 

 of lead are, however, secondary deposits derived from the decomposi- 

 tion of sulphides, whose age we are as yet unable to fix with perfect 

 certainty. Though in the case of the ores of Comillas — blende, galena, 

 and Smithsonite, or carbonate of zinc — the age of the hydrocarbonate 

 enables us to approximately fix that of the ores just mentioned. 



In August, 1867, I had an opportunity of seeing another in- 

 stance of Mammalian bones imbedded in mineralized matter, of even 

 more importance than the Udias fossils, because they occurred in a 

 regular vein containing galena, in carboniferous limestone. The mine 

 where the specimens which I now exhibit were found is one of a 

 group of mines around Stolberg, in Rhenish Prussia, and known as 

 the Albertsgmbe. The carboniferous limestone at this place, which is 

 not far from Hastenrath, forms a saddle, resting on Devonian sand- 

 stone. In this limestone five lodes are met with in the workings 

 at the Albert Mine. One of these, in its higher parts, consists of yellow 

 clay, more or less mixed with sand. Lower down calc spar in large 

 crystals, with imbedded crystals of galena, is associated with this clay. 

 Galena also occurs in the clay in lumps, which are often one hundred 

 pounds weight. This galena is sometimes associated with a kind 

 of hard calc sinter, and some granular concretions of cerussite, or 

 plumbic carbonate, are found on the galena. The latter mineral is also 

 found by itself in the clay, under circumstances analogous to those 

 under which it occurs in the mines of Santander ; it, however, gra- 

 dually disappears in depth. 



In a part of this vein, and at a considerable depth, a thin band 

 of what looks like the fine mud of very dense peat or brown coal, 

 more or less mixed with fine sand, occurs. This band is generally only 

 a couple of inches thick; but the coaly substance is here and there 

 diffused through the clay and sand for some extent. Some of the calc 

 sinter in its neighbourhood looks like a soft black limestone, owing to 



* " Proceedings of the Royal Irish Academy," vol. viii., p. 9. 

 f " Atlantis," vol. iv., p. 378. 



\ " Notes on the Geology and Mineralogy of the Spanish Provinces of Santander and 

 Madrid." London, 1863, p. 66. 



R. T. A. PROC VOL. X. 3 H 



