2 1 6 PREHISTORIC E UR OPE. 



But glacial moraines and rock-strise are not the only physical 

 evidence of a former general refrigeration of climate in Europe. 

 There are certain superficial phenomena which, although they 

 cannot be referred to the action of glaciers, are yet sufficiently 

 suggestive of colder conditions than the present. Of such a 

 nature are those massive " breccias " or agglomerations of angular 

 ddbris, and those more or less loose heaps and sheets of earthy 

 rubbish and rock-fragments, which occur in such bulk and in 

 such positions, as to show that they could not have been formed 

 under present conditions. A very good example of this is 

 furnished by the massive limestone-breccias of Gibraltar, which 

 have been described by Professor Eamsay and myself. 1 The 

 famous Eock is composed almost entirely of limestone-strata, 

 which generally dip at a high angle. It rises, as is well known, 

 in the form of a narrow sharp ridge, that shoots nearly south 

 into the Mediterranean. Inland it terminates in an almost per- 

 pendicular wall that rises to a height of 1349 feet. To the east 

 it presents " a bold escarpment, which is for the most part in- 

 accessible, and in places almost vertical, the cliffs where they 

 are lowest having a drop of not less than 300 or 400 feet, and 

 of more than 1000 feet where they approach the sea on the 

 north. From their base the ground falls rapidly away to the 

 coast-line, at angles that vary from 30° to 40°." The slopes 

 facing Gibraltar Bay are not so steep, as will be seen from the 

 accompanying section (Fig. 6), which gives the profile on a 

 true horizontal and vertical scale. The dominating point of the 

 Eock is 1396 feet. 



It will be observed that the limestone-strata (Z) dip steeply 

 to the west, where they are succeeded by beds of shale and thin 

 bands of grit and limestone at S. The " faults " or dislocations 

 I need not consider, as they are of older date than the phe- 

 nomena we are about to discuss. Eesting upon the surface of 

 the shale (S) will be observed a deposit marked B. This con- 

 sists of a heterogeneous accumulation of angular fragments and 

 blocks of limestone, embedded in a matrix of calcareous grit 



1 Quart. Journ. Geol. Soc, 1878, p. 505. 



