228 PATAGONIAN EXPEDITIONS: GEOGRAPHY. 



monize his conclusions, as set forth in the last clause of the second para- 

 graph quoted above, with the facts as stated in the last sentence of the 

 first paragraph? If, as he correctly states, the beds of bowlders form 

 opposite cliffs of the same valleys, how could he arrive at the "inevitable 

 conclusion," "that the formation of the great transverse valleys of Pata- 

 gonia w^as brought about by great dislocations and gigantic faults at a 

 comparatively recent geological period, posterior to the Bowlder (Shingle) 

 formation and at the last emergence of the land"? If such has been the 

 origin of these valleys, would we not now find both the beds of basalt 

 and the bowlder or shingle deposits separated on opposite sides of the 

 valleys by a vertical displacement equalling the amount of such fault, 

 instead of occupying directly opposite cliffs, as is the case? 



Throughout my travels in Patagonia I was impressed with the remark- 

 able uniformity of the strata at like horizons on opposite sides of the 

 same valley, wherever and whenever good sections were available. 

 Darwin, moreover, has observed and remarked upon this very question. 

 On page 119 of his Geological Observations in South America, he says 

 the land in this region has been upraised without the strata having been 

 in a single instance, as far as his observations went, unequally tilted or 

 dislocated by a fault. 



Dr. Ameghino's statement to the effect that "it is evident that if the 

 valleys had existed before the great marine submergence referred to, they 

 would have been completely filled with marine deposits, which, even sup- 

 posing they had been swept away afterwards by the waters, would always 

 have left numerous traces buried in the innumerable angles of the slopes," 

 is worthy of consideration. While it is evident that these valleys would 

 have received a deposit of bowlders equal to, or perhaps slightly exceed- 

 ing, that of the plains, it is not so evident, as he states, that they would 

 have been completely filled with a deposit which, as he says, was laid 

 down uniformly over the bottom of the sea, since these valleys are all of 

 them many times deeper than the thickness of the Shingle formation. It 

 is also evident, as he states, that had these valleys been in existence before 

 the deposition of the bowlders, remnants of this formation should still 

 be found in the innumerable angles of the slopes. Such remnants are not 

 only present on the slopes, as shown in Sections i and 2, but everywhere 

 over the surfaces of the terraced benches of the valleys, where they form as 

 conspicuous a feature of the surface as they do on the plains. No one 



