1 94 Scientific Proceedings, Royal Dublin Society. 



shingle times as that of a dry, probably warm, climate, with high winds; in 

 other words, an exaggeration of the climatic conditions which prevail at 

 present, with less snow and greater warmth. At present the summers of 

 Patagonia are very dry, and high westerly winds prevail ; great quantities of 

 dust are blown every year from the pampas into the Atlantic ; still very 

 little impression is made on the general outline of the country, as the surface 

 is everywhere protected, not only by a coarse grass and bush, but by twenty 

 odd feet of shingle which is spread over it. It is only near the settlements, 

 where the grass and scrub become eaten down and trampled away, that the 

 winds may be seen to make any impression, and it is from such places, and 

 from the roads which are now everywhere being made in the country, that 

 the chief part of the dust is derived. I am informed that a few years ago, 

 before this became a sheep-farming country, the grass was everywhere much 

 longer than it is at present, and consequently the protection to the surface 

 was greater. In the springs of the years, when the snow is melting, a certain 

 amount of erosion also takes place from the floods, but this only occurs in the 

 cafiadones and valleys, and even here very little cutting is found to have taken 

 place, except in those cafiadones where the surface has been broken by wheel- 

 tracks or other traffic. For instance, the winter of 1913 was a very severe 

 one, and there was much snow and rain, the floods in the spring being 

 enormous, and yet, on carefully examining quite a number of cafiadones 

 where there was no traffic, I was surprised to find that there was practically 

 no erosion of the surface, except a few tiny gullies, six inches wide and deep, 

 which would be obliterated with one month's dust and growth of vegetation. 

 Such winters occur only once in ten years as a rule, and hence the present 

 climatic conditions are incapable of producing the surface state of Patagonia 

 as we now find it. If, however, the shingle were removed, and the climate 

 slightly altered, so that the winters were more dry, and the winds in the 

 summer perhaps a little stronger, we should have all the conditions necessary 

 to produce that great flat country which must have existed in Patagonia in 

 pre-shingle days. 



It appears that after a long period of dry, windy climate, probably in late 

 tertiary times, the conditions began to alter, and that slowly, gradually, and 

 without violence the shingle began to creep down over the pampas until it 

 reached the Atlantic. No carving or cutting of the country took place during 

 this period, which probably lasted for a long time; in fact, at the end of the 

 great shingle period the country was probably as flat and even as before. 

 None of the great river valleys, in my opinion, existed then, and there were 

 probably no bajos. 



As we have seen, the Cape Fairweather Bed is a marine formation, 



