Notices of Memoirs — Miner alogical Observations. SI 9 



extensive gravel-pits are worked, as at Beeston and Sawley. The 

 pebbles and small boulders found in the gravels are very similar to 

 those found in the drift, of which some detached portions ma-y be 

 seen at New Basfovd, Lenton, Cinder Hill, and Annesley. In these 

 instances the drift lies immediately upon the Bunter Sandstone. They 

 are all in the Leen basin ; and supposing them to be of Post-glacial 

 age, they would seem to indicate a comparatively recent date (sjDeak- 

 ing geologically) for the present valley of that river, which is 

 certainly formed by the erosion of the Bunter, on which the drift lies 

 in elevated positions. The abundance of Bunter pebbles at present 

 scattered over the Permian strata in the Leen Valley affords corrobora- 

 tive evidence of this former extension of the Bunter strata. The 

 age of the Valley of the Trent is not so easily made out. From 

 the occurrence of drift on the higher portions of ground included 

 within its present basin, it would appear that the sculpturing of the 

 main features of the landscape began during or before the Glacial 

 Epoch. Great, however, as is the amount of alluviuin and low-level 

 gravel contained in the present valley, there can be little doubt that 

 this is now the redeposited drift, since bones of recent Mammalia have 

 been found in the river valley; notably in the sinking of the Wilford 

 Pit, where they lay at the very bottom of the alluvial deposits, 25 feet 

 below the surface. If, as it has been supposed, the Trent was once 

 a tributary of the Rhine, that will only carry us back (according to 

 Prof. Ramsay) to Miocene times. The question then arises whether 

 the time between that and the Drift period is sufficient to allow for 

 the denudation of the present area of Trent drainage, and the con- 

 temporaneous cutting down of the two passages through the Oolite 

 escarpment, one of which is now occupied by the Humber, the other 

 by the Witham at Lincoln. 



I. — MiNERALOGIOAL OBSERVATIONS IN THE ARGENTINE REPUBLIC. 



Mineralogische Beobachtungen im Gebiete der argentinischen 

 Republik von Alfred Stelzner. Mit chemischen Beitragen 

 von Max Siewert. Mineralogische Mittlieilungen, 1873, Heft iv. 

 pp. 219-254. 



IN this paper Dr. Stelzner, of Cordoba, records the results of his 

 mineralogical studies in certain parts of the Argentine Republic. 

 The value of the commmiication is much increased by the analytical 

 work contributed by Dr. Siewert. 



The Sierra of Cordoba, which stretches in a north and south 

 direction over nearly three degrees of latitude, is formed of three 

 parallel ridges, of which the central and most lofty, called the Sierra 

 Alta, rises to a height of about 1200 metres above the surrounding 

 pampas. These mountains consist essentially of crystalline slates, 

 associated with granite and other rocks. The gi'anite is penetrated in 

 many places by quartz-stocks, which are interesting for the sake of 

 the accessory minerals they carry. Although consisting mainly of 

 quartz, they invariably contain mica and large crystals of orthoclase ; 

 and may thus represent a highly quartziferous variety of pegmatite. 



