42 PATAGONIAN EXPEDITIONS : NARRATIVE. 



the spring gushes from beneath the bed of shingle overlying the tosca, when 

 I sat down for a moment's rest, I was immediately struck with the variety 

 and number of the birds about me, more especially since during our trip 

 across the pampa we had been impressed with the scarcity of bird life. 

 Nearby were a number of calafate and incense bushes, and about these 

 were to be seen the red-breasted meadow lark, Trupialis militaris, some- 

 what larger than our yellow-breasted forms. The little crested song 

 sparrow, Zonotrichia canicapilla, was everywhere about, as was also a small 

 yellow-breasted finch, Chlorospiza melanodera, while in the dense foliage 

 of the clumps of mata verde and mata negra that grew everywhere a little 

 brown wren, Troglodytes horhensis, could be seen hopping about in the 

 manner so characteristic of these birds. The several and deeply worn 

 game trails that radiated from this spring bore unmistakable evidence that, 

 prior to the time of the building of the shanty, this had been a favorite 

 watering place for the bands of guanaco, rhea, and other larger mammals 

 and birds indigenous to the region. 



A hasty examination of the spring convinced me that the shingle was 

 the source of the water supply, and the appearance of the latter at the surface 

 indicated the point of contact between the shingle and the underlying tosca. 



On turning my attention to the great depression before me, it was 

 readily apparent that, while it was surrounded on all sides by high bluffs, 

 these were decidedly higher to the westward than to the eastward, and 

 by a subsequent study of this and hundreds of other similar depressions 

 found scattered throughout the Patagonian plains I arrived at the con- 

 clusion that such depressions were once bays formed during the progress 

 of the final recovery of this region from the sea and were formerly quite 

 similar to San Bias, New Bay, San Julian and Peckett Harbor. As the 

 elevation proceeded, such bays were transformed first into lakes by being 

 cut off from the sea. Later, such lakes became entirely desiccated, or 

 more or less reduced in size, according as the water supply from their 

 tributaries compared with the loss by evaporation. The full discussion 

 of the origin of these depressions will be left to the chapters on the 

 geography and the geology of the region. 



From the shepherd's house the trail led out across the valley for a few 

 miles, then up the side of the bluff to the plain lying to the north of the 

 depression, which was noticeably lower than that to the west. In a short 

 time we had crossed this plain and, coming to its northern crest, looked 



