SOME GEOLOGIC ASPECTS OF CONSERVATION 
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a gushing stream of beautifully clear cold water which issues 
from a similar, though probably smaller, rock-encumbered cavern 
not far from the Ice Cave. In times past the stream from the 
spring built up a deposit of tufa at the mouth of the little 
ravine down which it flows. There are countless other beautiful 
springs in the region and indeed every valley and ravine is a 
dream of beauty with flowing stream and towering castellated 
walls clothed with the beautiful green of summer or the glow- 
ing colors of autumn. 
Fig. 10. Islands .and ponds in the Mississippi below McGregor. 
In a land of universal charm a spot which stands out with 
especial clearness in the memory of the traveler is the region 
around McGregor and North McGregor, the region in which it 
is now proposed to establish a national park. Especially favored 
by lavish Nature as to river, rock and bluff its charm is never- 
ending and its quiet beauty makes an impress which lingers 
through the years. The Pictured Rocks, about a mile below 
McGregor, are an unusual phenomenon even in this land of 
the unusual. A hundred feet or more of St. Peter sandstone, 
stained with all the browns and reds and yellows and purples 
of the iron oxides, in contrast with the translucent white of the 
