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Sierra Club Bulletin. 



law in their arrangement, nor anything else imme- 

 diately suggestive of their mode of origin. The ma- 

 jority occur in loosely connected groups, but some lie 

 off by themselves, like pale islands in a dark ocean. 

 As the view in Fig. i well shows, they generally com- 

 mence abruptly and terminate abruptly, without definite 

 relation to the unevennesses of the floor itself. Some 

 divide, others merge downward; some gain in width, 

 others taper down toward their lower ends. 



In dimensions they are equally varied. While they 

 average between four and five feet in length and from 

 two to three inches in breadth, there are individuals 

 among them but a fraction of a foot long and others 

 exceeding twelve or even fifteen feet; and some are 

 less than an inch across, while others — like those in 

 the immediate foreground of the view — span six inches 

 and over. Nor is the breadth always proportionate to 

 the length. Some of the longest are very narrow, 

 some of the shortest very broad. 



On closer inspection they are seen to consist simply 

 of narrow tracts from which the lichens that otherwise 

 uniformly mottle the rock have been removed, and it 

 becomes plain that it is merely the light color of the 

 unweathered granite thus exposed that makes them 

 prominent. These stripes, then, are not stains at all; 

 rather, they owe their brilliancy to their very stain- 

 lessness — to the absence of coloring matter of any 

 sort. 



By what agent the lichens were cleared off, how- 

 ever, seems at first a mystery. That it was some sub- 

 stance that moved downhill under the influence of 

 gravity is patent from the invariable downhill trend 

 of all the stripes, but what the nature of that substance 

 was, is not easily guessed. One feels tempted to be- 

 lieve it was some corrosive fluid that was poured out 

 upon the rock and flowed down slowly, eating away 

 the lichens as it went. There are places in the 

 Yosemite Valley where such a thing has actually hap- 



