I 70 PATAGONIAN EXPEDITIONS : NARRATIVE. 



when, aroused from my reveries and wrapped in saddle blanket and slicker, 

 I gave myself up to sleep. 



The next morning I continued my journey to camp, stopping long 

 enough to examine a thick layer of basalt which cropped out just below 

 the top of the bluff and was overlaid by the glacial deposit already men- 

 tioned as occurring on the summit. On my return to camp I left the 

 glacial hills and entered the broad valley of Spring Creek, just at a point 

 where there were a number of fine springs. Here I decided to establish 

 our next camp, until such time as I should be able to examine the coun- 

 try some thirty to forty miles to the westward in the vicinity of Lake 

 Pueyrredon, where from a distance I had already observed that there 

 were considerable exposures of what appeared to be sedimentary rocks. 



On the morning of the following day we moved across the valley of 

 Spring Creek, camping at the springs just mentioned. That same after- 

 noon I started for Lake Pueyrredon, intending to return the following 

 day. Holding a more westerly course than I had done on the last ex- 

 cursion, I descended into the valley some three miles east of where Rio 

 Blanco enters it, after emerging from a canon in the southern border. 

 For some distance after entering the valley this river flows along over a 

 shallow, rocky bed, before entering the deep and narrow cailon cut in the 

 glacial drifts a few miles below. Crossing this stream I directed my 

 course for a bare rocky elevation lying between White Lake and the 

 eastern extremity of Lake Pueyrredon, which I reached late in the after- 

 noon. Directly opposite this point a small river, which I have called the 

 Rio Tarde, for want of a better appellation, after emerging from one of 

 the most picturesque caiions in this region, turns abruptly to the westward 

 and empties its waters into Lake Pueyrredon. The valley here has a 

 width of perhaps not more than five miles, and is for the most part well 

 watered and grassed. Unsaddling and caring for my horse, I set out to 

 examine the nature of the rocks constituting the mountain mass lying 

 between White Lake and Pueyrredon. I found these to consist prin- 

 cipally of variously colored sandstones and porphyries, frequently of 

 most brilliant colors, and among which certain masses of a peculiar green 

 color predominated. The character of this rock was in every way similar 

 to those pebbles described by Darwin as of a gall-green color and so 

 abundant over certain regions in the shingle of the plains near the coast. 

 There is little doubt that this was the source of many of the pebbles seen 



