174 PATAGONIAN EXPEDITIONS: NARRATIVE. 



looking about I was not long in discovering a number of others scarcely 

 less interesting, which, for obvious reasons, I was compelled to leave 

 behind. 



As I continued my journey, arriving finally at the extreme summit of 

 the bluff shown in Fig. 14, there appeared spread out before me a bad- 

 land area several square miles in extent. The higher peaks of these 

 bad lands I afterwards discovered to be capped with some three hun- 

 dred feet of marine deposits, which, as mentioned above, belonged to the 

 Cape Fairweather beds, according to Ortmann and Pilsbry, of Pliocene 

 age. Through what enormous physical changes has the crust of the earth 

 passed in this region within comparatively recent times ! Here on the 

 very slopes of the eastern range of the Andes, at an altitude of more than 

 five thousand feet above the present sea level, are from two to three hun- 

 dred feet of marine deposits of Pliocene age conformably overlying fifteen 

 hundred feet of fresh-water, or perhaps in part, aeolian deposits. And, 

 moreover, the thickness and nature of these deposits, remarkably free 

 from any coarse conglomerates, is such as would indicate that the birth 

 of the Andes took place at the close of the Pliocene and that during the 

 deposition of the Cape Fairweather beds a continuous, though shallow, sea 

 prevailed over at least most of the region now occupied by the snow- 

 capped peaks and ranges of the southern Andes, while during the Santa 

 Cruzian period the same region was occupied by a broad, low and level 

 land with numerous and, for the most part, small lakes, connected by 

 sluggish streams and separated by broad marshes and uplands. At that 

 time this region was inhabited by the birds and mammals whose remains 

 are now found in such abundance in the sandstones and clays, in which 

 they became imbedded, as the latter were laid down over the bottoms and 

 flood-plains and along the shores of these prehistoric lakes, rivers and 

 marshes. Where, then, it may be asked, was the land-mass from which 

 were derived the materials composing these deposits ? This and other 

 questions will be considered when I come to discuss the geology of the 

 region. 



That at some past time, the five thousand feet of sedimentary deposits 

 forming the bluff on which I stood had extended northward across the 

 valley, was plainly evident from the nature of the surrounding country. 

 That the valley had been formed by erosion was also evident. It was 

 clear then that, since the close of the deposition of the Cape Fairweather 



