SHELL GAP. 127 



a large circular basin, which lay just at the foot of the Andes and was 

 partially surrounded, especially on the south, by bare, white, bad-land 

 hills. The extensive and promising nature of these exposures led me to 

 decide upon entering the Cordilleras by way of the southernmost of these 

 two branches of the river. After examining some small exposures of 

 sandstone on the side of the hill at the summit of which I had been 

 standing, without arriving at any very satisfactory conclusion as to their 

 exact nature, I returned to camp and the following morning we resumed 

 our journey up the river toward the foot of the mountains. 



We crossed the river almost immediately and continued to travel 

 throughout the day on the north side, camping at night alongside a beau- 

 tiful spring of clear water which came boiling up from a bed of almost 

 pure white sand at the bottom of a deep hole, some ten or twelve feet in 

 diameter, and flowed away across the meadow land which lay between us 

 and the river, in a brook of no inconsiderable dimensions. Hardly had 

 we halted and began unhitching our horses from the cart than a carrancha 

 came and perched himself at the top of a calafate bush so aggressively 

 near that, out of sheer wantonness, I am forced to admit, I drew my six- 

 shooter from its scabbard and, just to keep my hand in, dropped him life- 

 less to the ground beneath. 



The following morning we resumed our journey at an early hour and 

 about the middle of the forenoon recrossed the stream some distance 

 above the forks last mentioned and continued our westerly course along 

 the north bank of the more southern of these two forks. Since leaving 

 the old Indian trail the nature, both of the valley and its surface, had com- 

 pletely changed. Instead of the deep and narrow basaltic carton with a 

 perfectly level bottom covered with loose sand and shingle, there was a 

 broad, open valley with low, rounded glacial hillocks interspersed between 

 extensive tracts of bright green meadow lands, dotted over with small 

 glacial lakes and surrounded by high rolling hills. 



Long after noon we arrived at a narrow gap cut by the stream in a low 

 ridge of sandstone belonging to the Patagonian formation. So narrow 

 was this gap that we had to take to the bed of the stream, in order to pass 

 through it with our cart to the broad open basin that lay beyond. Since 

 the surface of the valley over which we had been travelling during the 

 early morning had been very rough, we decided to give our horses a short 

 rest and spend the time ourselves examining the rocks constituting the 



