224 Scientific Proceedings, Royal Dublin Society. 



the Gallegos Chico, almost filling it from side to side, except where the 

 present river has cut a recent narrow gorge, is found a most perfect 

 little terminal moraine. In PL VII, fig. 4, we are looking across the mouth 

 of this valley, and it will be seen that the moraine almost closes it. The 

 present river has cut its way through it, and is running down in a narrow 

 channel a little beyond the horses. I consider this moraine, although very 

 small, most instructive, as it clearly shows that the great erosive action which 

 operated intermittently over an extensive period in the cutting out of the river 

 valleys was accompanied to its termination by the periodic advance of ice in 

 the form of glaciers ; and this confirms my already expressed belief that all the 

 terraced river valleys are fluvio-glacial products even down to their lowest 

 levels. 



Although I have abundantly looked for it, I have never succeeded in 

 finding anything that would show that during the inter-glacial periods the 

 climate was as genial as at present. 



There is everywhere in the country evidence of oscillations of climate, but 

 I have never found any facts which would prove beyond doubt that there 

 was a true inter-glacial epoch. In every terrace I have been able to examine 

 the shingle lies directly on the underlying tertiary rock, and I have never 

 seen any deposit of loam or mud, with animal or plant remains, intervening 

 between them. I have found at least four separate deposits of moraine 

 material, each of them belonging to a different horizon, and probably many 

 more might be found if a systematic search could be made. 



The first I found was, as I have already described, the great terminal 

 moraine on the high pampa, from which ran the supra-pampean shingle- 

 layer as an outwash. The second was on a high terrace at the back of 

 Bella Vista, and it was cut into when the river valley was lowered to 

 tlie next lower level. The third was an extensive terminal moraine about 

 fifteen miles to the west of Douglas Estancia. Finally, I found, as men- 

 tioned above, a very well-marked small terminal moraine filling the mouth 

 of the Gallegos Chico river valley, where it opens into the Gallegos river,- 

 and having its base almost on the present level of the latter. Now, the 

 Gallegos Chico valley is cut down through over two hundred feet of 

 Buitreras bed, which, we have already seen, was probably formed on the 

 floor of an inter-glacial lake. This shows that at the very end of the river- 

 valley period, when their beds had been lowered to their present levels,, 

 tongues of glacier extended into the river valleys as far to the east as the 

 first great plateau glacier which gave origin to the pampa shingle. 



The diagrammatic section through this portion of Patagonia from west to- 

 east shows the position of these four moraines. 



