Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/223

 mood to visit the Torcal, and hope that soon some abler pen may do full justice to its merits.

As soon as our first impression had subsided, we began to speculate upon the causes which had made the rocks assume such a fantastic shape. "We all agreed that it must have been an effect of denudation ; in what particular way, however, we could not determine, although we were inclined to ascribe it to an ancient glacier : this opinion appeared to acquire some support when we found, on our descent, some rocks detached and separated a long way from the general mass, which we considered to be erratic blocks carried down by the action of ice. However, not being satisfied with this conclusion, and desiring to study the phenomena of the place with more attention, some of us returned there ; and by starting before daybreak from Antequera we were able to remain several hours on the Torcal, and had more time for observing the form and composition of the rocks.

In order to convey to you the best idea that I can of these formations, I shall begin with the plain of Antequera, which, in our rapid excursions through it, we considered to belong to the Tertiary period. The soil of the southern part of the city consists of a dark blue and compact limestone, in a semicrystaline state, which is overlapped on the northern side by a coarse and fragile rock, also calcareous, with a certain mixture of sand, seeming to me to be analogous to the " Calcaire grossier" of the Paris basin. This stratum dips to the south ; its thickness is rather considerable — I believe, reaching twenty or thirty yards. It contains many fossils, principally the casts of an Arca, which are very abundant. In the same valley, in a place called Castillon, about three miles west of Antequera, at the site of an ancient Roman town named Singilia, I have found many fragments of a beautiful marble, entirely composed of shells of Foraminifera — I believe, of the same kind as that which Sir Charles Lyell describes in page 301 of the sixth edition of his ' Elements,' under the name of Miliolite limestone. I had no opportunity of ascertaining the position of the blocks from which these fragments were detached ; they were wrought remains of ancient buildings ; but, considering their abundance, I came to the conclusion that their quarry could not be far off. We have also in this neighbourhood the same Miliolite limestone, in concretion with another calcareous stratum, containing many Nummulites (said also to be found near Antequera, although I have not met with them myself) ; and it is probable that both may belong to the same period, and that this may be either the Middle or the Lower Eocene. I see this is also the opinion of M. de Verneuil ; for in his map he classifies the plain of Antequera as " Tertiaire inferieure," although he does not seem to have found any Nummulites ; for that portion of his map does not contain the sign which indicates their presence. Between Antequera and the Torcal there is another calcareous formation, containing many forms of Gryphoea ; it is above the blue limestone, and of very limited extent.

The Torcal rises abruptly from the plain of Antequera, its north-