190 Scientific Proceedings, Royal Dublin Society. 



After travelling a certain distance, however, over the plain, the monotonous 

 scene depicted above may change without warning. Suddenly a huge valley 

 may be found to lie below us, hundreds of feet deep, extending for rjailes, and 

 eventually rising once more in the distance to the original level. 



Along the bottom of this valley, which will be found to run from west to 

 east, a small and, comparatively speaking, insignificant river will in most 

 cases be observed, flowing sluggishly in various sinuous curves, and small, 

 out of all proportion, to the size of the valley in which it is found. These 

 river valleys begin, as a rule, among the hills to the west, and extend to the 

 Atlantic ; but besides these, we occasionally come across other valleys which 

 are found, after being followed for some miles, to begin blindly, and end in 

 the same manner; in fact, tiiey are hollow, cup-shaped, or, more correctly 

 speaking, dish-shaped, depressions scooped out of the pampa, and have in 

 their lowest parts, instead of a river, as a rule, one or more salt lagoons. These 

 are the "bajos " of Patagonia, and are some of the most puzzling features found 

 in the district. There are also numbers of long, more or less narrow valleys 

 styled " canadones," running as tributaries to the river-valleys and bajos. 

 These vary in size, and often cut deeply back both to the north and south 

 into the pampas. Sometimes they run for many miles, and although, as a rule, 

 they are dry, at times a small stream runs down the centre. 



In this eastern portion of Patagonia no trees are ever found either on the 

 pampas, valleys, or canadones, but the surface of the ground is everywhere 

 clothed with a coarse grass, and in places with a scrubby bush a foot or two 

 in height. The condition is one found generally in steppe countries. 



The descent from the higher valleys to the river level below is not in the 

 form of an inclined plane, but in a series of steps or terraces. These latter 

 vary in number in different localities ; in some places there are seven, in others 

 only one or two, whereas in others we may find the pampa falling direct in one 

 drop to the river below. 



Besides this condition of extreme flatness which I have mentioned, we 

 shall also see, if we examine fig. 1 carefully, that there is evidence of con- 

 siderable erosion having taken place in the surface of the country as well as 

 the levelling action. 



In the foreground of fig. 1 we are looking across a large cariadon which 

 has eaten back into the country from the Atlantic. Now, if we come down 

 on to one of the terraces we may possibly see a peculiar flat-topped hill 

 standing out in a very bold manner some considerable distance, perhaps a 

 mile or so from the edge of the pampa. The level of the top of one of these 

 hills is found to be the same as the general plane of the pampa ; in fact, the 

 hill is an isolated portion of the pampa which has been able to resist the great 



