pose. The description of Dr. Peale is interestingly comprehensive, 

 and is as follows : " This is one of the most beautiful springs in the 

 Upper Basin. It has a delicate rim, with toadstool-like masses 

 around it. The basin slopes rather gently toward a central aperture, 

 that, to the eye, appears to have no bottom. The water in the 

 spring has a delicate turquoise tint, and as the breeze sweeps across 

 its surface, dispelling the steam, the effect of the ripple of the water 

 is very beautiful. The sloping sides are covered with a light brown 

 crust ; sometimes it is rather a cream color. The funnel is about 

 40 feet in diameter, while the entire space covered by the spring 

 is about 55 X 60 feet, outside the rim of which is a border of pitch 

 stone (obsidian) sand or gravel, sloping 25 feet. From its west 

 side flows a considerable stream, forming a most beautiful chan- 

 nel, in which the coloring presents a remarkable variety of shades ; 

 the extremely delicate pinks are mingled with equally delicate tints 

 of saffron and yellow, and here and there shades of green." 



The overflow from this spring spreads out over a large area, called 

 Specimen Lake, where absorption of the silica from the water has 

 destroyed many of the trees of the vicinity, the dry, lifeless trunks 

 adding to the attractiveness of the place by affording the appear- 

 ance of petrifactions.^ All of these exquisite masses of colors which 

 are found lining the pools, filling the overflow channels and spread- 

 ing out flat in the lower marshy places, are due to the growth ot 

 vegetal organisms belonging to the bacteria and alg?e. 



Walter H. Weed- describes the appearance of the Black Sand 

 Basin and channels filled with algal growths : " As the water from 

 this spring flows along its channel it is rapidly chilled by contact 

 with the air and by evaporation, and is soon cool enough to permit 

 the growth of the more rudimentary forms which live at the highest 

 temperature. These appear first in skeins of delicate white filaments 

 which gradually change to pale flesh-pink farther down stream. As 

 the water becomes cooler, this pink becomes deeper, and a bright 

 orange and closely adherent fuzzy growth, rarely filamentous, 

 appears at the border of the stream, and finally replaces the first- 

 mentioned forms. This merges into yellowish-green, which shades 

 into a rich emerald farther down, this being the common color of 

 fresh-water alg.x. In the quiet waters of the pools fed by this stream 



^ Haynes-Guptill, Guide to Yellowstone Park, p. 68. 



* Weed, Ninth Annual Report U. S. Geological Survey, p. 657. 



