Vol. 63.'] RAISED BEACHES OF TALTAL. 67 



rough but effective filters, blocks of the ' losa ' being cut into the 

 shape of hollow cones. I do not know that any explanation of this 

 structure has yet been advanced, but I hazard the suggestion that 

 it involves the solvent action of percolating rain-water upon 

 aragonite-shell, and the subsequent deposition of the carbonate of 

 lime in the form of the more stable calcite. 



Another feature due to the recent elevation of the coast relative 

 to the present sea-level may be mentioned. The massive rocks of 

 the coastal region are traversed by innumerable steep-walled 



* quebradas' or ravines, formerly carrying torrents but now almost 

 wholly dry. Prom what I could learn from old residents, it is only 

 at rare intervals that sufficient rain falls to permit of the temporary 

 formation of streamlets reaching the sea ; and, generally, it may be 

 said that erosive action due to atmospheric water is almost at a 

 standstill in this part of the coast. The existence of these profound 

 ravines may be brought forward as a strong argument in favour of 

 a more humid climate in the Atacama Desert at a former period than 

 now. The feature to which I refer, is the manner in which the beds of 

 most of the minor quebradas suddenly alter in inclination and become 

 precipitous as they approach the sea. Were streams suddenly to 

 start running in these old gorges, they would terminate in water- 

 falls. In the larger and more open quebradas, of which the beds 

 are less inclined, this feature, if it exists, is hidden under the 

 accumulations of gravel previously described as the coastal plain. 



Where the small and steep ' quebradas ' debouch upon the plain, 

 they cut through the terraces and plain of the superficial formation 

 and lay bare the rock-floor. If we take into consideration the com- 

 parative inactivity of the erosive agencies, this fact would appear to 

 indicate that the shell-terraces thus cut through are of considerable 

 antiquity. They certainly all existed prior to the Spanish occupation, 

 since they are covered with the graves, implements, pottery, and 



* kitchen-middens ' of the now extinct Changos, who never, as a 

 people, got beyond the Stone-age culture. There are no graves 

 below the 15-foot terrace. On the other hand, arrow-heads and 

 flakes of chalcedony, sometimes actually rounded and rolled, are 

 numerous immediately above the present beach and almost within 

 reach of exceptionally -heavy surf ; but whether or no they have 

 travelled down from the upper level, it would be difficult to decide. 



It may, perhaps, not be out of place to mention in conclusion 

 that certain beds found at great altitudes, as at Talcahuano, which 

 have been cited as proofs of a recent elevation to this extent, can, I 

 think, be shown to be accumulations of human origin. In two such 

 instances I found pottery and stone-implements mingled with the 

 shells, in such a manner as to suggest that the latter formed part 

 of extensive 4 kitchen-middens.' Having thus learned caution, I 

 think that some of these recent shell-beds at an elevation of 

 1000 feet and upwards might repay re-examination. 



