1 82 PATAGONIAN EXPEDITIONS: NARRATIVE. 



filled the great valleys of erosion which had previously been carved in 

 the surface of the latter, and permanently dammed the courses of the 

 streams by the deposition of moraines, left at successive stages during the 

 recession of the ice. 



The walls of these canons consist of a rather complicated series of igne- 

 ous and crystalline rocks. The region bears evidence of having formed a 

 land-mass during late Cretaceous and Tertiary times. In the walls of 

 the present cafions were to be seen numerous ancient valleys cut deep 

 into the surface of the older rocks, their troughs now filled with materials 

 belonging to the Cretaceous or to the Patagonian and Santa Cruzian Ter- 

 tiaries. Climbing to the summit of a particularly lofty, though isolated 

 and limited table, I observed that to the east, north and south the same 

 topographical conditions prevailed, and I was somewhat unwillingly forced 

 to the conclusion that, during middle Tertiary times, this region existed 

 either as a great island, or a narrow extension consisting of a chain of 

 islands, belonging to a former great continental land-mass and surrounded 

 by a shallow sea, over the bottom of which were deposited the Patagonian 

 beds. In the later Santa Cruzian epoch this region became more elevated 

 and the island, or islands, appeared as a low mountain range above the 

 surface of a broad, level plain. It was then that erosion began and con- 

 tinued somewhat interruptedly, until it has produced the present deeply 

 dissected condition of the country under consideration. 



During my lonely wanderings through these deep and tortuous canons 

 I naturally met with many interesting things and some novel, though not 

 always pleasant, experiences. Sometimes it would be the rescuing of 

 myself and horses from the mire of a not very inviting swamp, through 

 which we had essayed to pass to the bluff which lay at only a few hun- 

 dred feet beyond, rather than submit to a circuitous journey of several 

 miles. At other times, and all too frequently, the ascent or descent of 

 the caiion walls was not without its perils and imparted a certain spirit 

 of adventure to the work. This acted as a tonic and gave even a greater 

 zest to its accomplishment. On one occasion, when I had camped for the 

 night at the bottom of a particularly deep and narrow gorge where, how- 

 ever, there was a small stream and a plentiful supply of grass, I was 

 startled from a sound slumber by the sudden stampeding of my horses. 

 One of these I had left loose, while picketing the other, as had been my 

 custom. It was with some alarm that I heard the two animals go dashing 



