166 FKAGMENTS OF SCIENCE. 



rated from each other by places of dislocation, where the 

 strata are much wrenched and broken. These are 

 called the Northern and Southern Quebrada, from the 

 Spanish ' Tierra Quebrada,' or broken ground. It is at 

 these places that the inland caves of Gibraltar are 

 almost exclusively found. Based on the observations of 

 Dr. Falconer and himself, an excellent and most in- 

 teresting account of these caves, and of the human 

 remains and works of art which they contain, was com- 

 municated by Mr. Busk to the meeting of the Congress 

 of Prehistoric Archaeology at Norwich, and afterwards 

 printed in the c Transactions ' of the Congress. 1 Long 

 subsequent to the operation of the twisting force just 

 referred to, the promontory underwent various changes 

 of level. There are sea-terraces and layers of shell- 

 breccia along its flanks, and numerous caves which, unlike 

 the inland ones, are the product of marine erosion. The 

 Ape's Hill, on the African side of the strait, Mr. Busk 

 informs me has undergone similar disturbances.* 



In the harbour of Gibraltar, on the morning of our 

 departure, I resumed a series of observations on the 

 colour of the sea. On the way out a number of 

 specimens had been collected, with a view to subsequent 

 examination. But the bottles were claret bottles, of 

 doubtful purity. At Gibraltar, therefore, I purchased 

 fifteen white glass bottles, with ground glass stoppers, 

 and at Cadiz, thanks to the friendly guidance of Mr. 

 Cameron, I secured a dozen more. These seven-and- 



1 In this essay Mr. Busk refers to the previous labours of Mr. 

 Smith, of Jordan Hill, to whom we owe most of our knowledge of 

 the geology of the rock. 



2 No one can rise from the perusal of Mr. Busk's paper without 

 a feeling of admiration for the principal discoverer and indefa- 

 tigable explorer of the Gibraltar caves, the late Captain Frederick 

 Brome. 



