526 A. C. RAMSAY AND J. GEIKIE ON 



4. Alameda Sands. 



The low ground on which the greater part of the town of Gibral- 

 tar is built consists of more or less incoherent red siliceous sand. 

 Prom information supplied by Mr. E. Roberts, these deposits are 

 indicated on the map as stretching inland as far as Engineer Lane, 

 Governor's Street, and the Town Range Barracks. They occur all 

 over the area occupied by the Grand Parade and the Alameda Gar- 

 dens ; but no good sections are now visible. Some shallow pits and 

 holes in the Gardens showed unconsolidated red sand, with faint 

 traces of bedding, but no marine shells. In some parts they strongly 

 resembled the red earth which is found lying in holes and crevices 

 in the limestone. Erom their position, the Alameda Sands may 

 reasonably be inferred to be of marine origin, modified perhaps to 

 some extent by subsequent iEolian action. They go up to a height 

 of 160 or 170 feet. 



5. Catalan Sands, SfC 



One of the most striking features of the promontory is the great 

 bank of sand and debris which clothes the whole eastern flanks of 

 the Rock from the North Eront south to beyond Sandy Bay. Erom 

 the base of the great cliff of Middle Hill and the Signal Station the 

 slope sweeps down to the coast at an average angle of not less than 

 34°, the fall being as much as 700 feet. The slope consists in chief 

 part of sand, with here and there scattered blocks and fragments of 

 limestone. It is evident, however, that much limestone -agglomerate 

 and many fallen masses of limestone underlie it. These are seen 

 projecting above its surface here and there, especially at Catalan 

 and south of Sandy Bay. At both these places, in fact, the sand 

 merely lies amongst and between great blocks of limestone and 

 masses of agglomerate and debris. The sand is composed of quartz 

 granules and comminuted and worn fragments of shells, the mass 

 being here and there partially hardened by infiltration. In such 

 places the hardened layers stand out in relief in the same way as in 

 the case of sandstones which have weathered unequally. Much of 

 the sand is very coarse and gritty. 



6. Later Limestone-agglomerates. 



We pass on now to describe those masses of limestone-agglomerate 

 which are found resting upon recent marine deposits and eroded 

 limestone-platforms or terraces. The agglomerates now referred to 

 are similar in most respects to the older accumulations of Buena 

 Vista. Like them they are made up of angular fragments of lime- 

 stone of all sizes, up to blocks several yards in diameter, set in a 

 calcareous earthy matrix, which is either red or grey. In none of 

 them, however, did we detect any trace of bedding ; they are mere 

 rude jumbled masses piled up along the base of more or less promi- 

 nent cliffs, from which they slope gradually outwards. 



