Ixxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



which prevail throughout these formations. The direction of the 

 principal mountain- chain -which traverses the peninsula from Lisbon 

 to the Pico de Grado, passing through the provinces of Segovia, 

 Soria, and Guadalajara, is from E. 27° N. to W. 27° S. ; four other 

 important mountain- chains run nearly parallel to it, although slightly 

 obliquely. The author then, taking up the views of M. Elie de 

 Beaumont, endeavours, I think somewhat hastily, to refer these dif- 

 ferent lines of elevations to the diiferent systems laid down by the 

 great Erench geologist in the European region-: thus he refers the 

 chains of the Guadarama, La Gata, and La Estrella, the mean direc- 

 tion of which is E. 39° N., to the System of "Westmoreland, which 

 throughout Europe oscillates between N.E. and E.N.E. But it is 

 unnecessary to pursue this question any further. 



Cretaceous formation. — In the district under consideration Don 

 Casiano has found only one of the four groups into which M. 

 d'Archiac divides this formation, namely, the Lower Chalk {craie tuf- 

 feau), the second in descending order. He has found no trace either 

 of the white chalk immediately above, or of the gault immediately 

 below, or of the fourth or lower group. It is found only in narrow 

 and contorted bands in certain spots ; this is aU that remains of 

 the greater extent of ground it must have originally covered, except 

 such portions as may be concealed by the Tertiary and Quaternary 

 deposits, and which towards the south may extend continuously into 

 the province of Cuenca. There is no appearance that the Cretaceous 

 sea ever extended further west than the Mota del Cuervo in this 

 last-mentioned province, orQuintanar de la Orden in that of Toledo, 

 or Quijorna in that of Madrid, Espinar in that of Segovia, or the 

 river Luna in the province of Leon. In this ancient sea the Sierra, 

 or mountain-chain of Guadarama, formed one peninsula, which termi- 

 nated towards the east. Hot far from the Picode Grado, and another 

 smaller, within the province of Madrid. The author then describes 

 the different bands which he has examined; their dip is generally. 

 S.E., and they are of no very great breadth or length, but are natu- 

 rally broader where the dip is less. One of these bands, in the 

 neighbourhood of Atalaya del Yellon, has been broken through at 

 the spot where its strike is curved round, forming a gorge of a few 

 metres in breadth, at the bottom of which the mica schist (micacita) 

 on which the chalk rests is exposed. 



The prevailing rock in this formation is limestone, varying much 

 both in colour and in structure,. being occasionally quite spathose or 

 crystalline ; very little of it can be used either for building-pur- 

 poses or for lime. It is sometimes argillaceous or marly. Chalk- 

 marl occurs in some of the beds, as well as sandstones, apparently 

 Greensand. In this and in the lower beds a few traces of lignite 

 occur, which in former times, and especially" in the reign of Charles 

 III., gave rise to the most extravagant expectations respecting the 

 coal of Manzanares, which was said to be superior to that of En- 

 gland, because it contained more sulphur! The greatest thickness of 

 the Cretaceous formation is about 300 metres, but in many places it 

 has been reduced by denudation to from 20 to 2b and even 17 metres. 



