Studies in the Sierra 



83 



ter snow, severe rain-storms, and by floods of exceptional pow- 

 er, produced by rare combinations of causes, which in the Si- 

 erra occur only once in hundreds of years. So vast is the dif- 

 ference between the transporting power of rivers in their ordi- 

 nary every-day condition and the same rivers in loud-booming 

 flood, that no definite gradation exists between their level silt- 

 beds and rugged boulder deltas. The ordinary power of Sierra 

 streams to transport the material of boulder soils is very much 

 overestimated. Throughout the greater portion of their chan- 

 nels they can not, in ordinary stages of water, move pebbles 

 with which a child might play; while in the sublime energy of 

 flood they toss forward boulders tons in weight without any 

 apparent effort. The roughly imbricated flood-beds so com- 

 monly found at the mouths of narrow gorges and valleys are 

 the highest expressions of torrential energy with which I am 

 acquainted. At some time before the occurrence of the grand 

 soil-producing earthquake, thousands of magnificent boulder- 

 beds were simultaneously hurried into existence by one noble 

 flood. These ancient boulder and cobble beds are distributed 

 throughout the deep valleys and basins of the range between 

 latitude 39° and 36° 30' ; how much farther I am unable to say. 

 They are now mostly overgrown with groves of oak and pine, 

 and have as yet suffered very little change. Their distinguish- 

 ing characteristics are, therefore, easily readable, and show 

 that the sublime outburst of mechanical energy developed in 

 their creation was rivaled only in the instantaneous deposition 

 of the grand earthquake beds. 



Notwithstanding the many august implements employed as 

 modifiers and reformers of soils, the glacier is the only great 

 producer. Had the ice-sheet melted suddenly, leaving the 

 flanks of the Sierra soilless, her far-famed forests would have 

 had no existence. Numerous groves and thickets would un- 

 doubtedly have established themselves on lake and avalanche 

 beds, and many a fair flower and shrub would have found food 

 and a dwelling-place in weathered nooks and crevices. Yet the 

 range, as a whole, would seem comparatively naked. The tat- 

 tered alpine fringe of the Sierra forest, composed of Pinus 

 Hexilis and P. aristate, oftentimes ascends stormy mountain 

 flanks above the upper limit of moraines, upon lean, crumbling 



