PUBLIC PARKS OF IOWA 271 



away loose sand or solid ledge until the present picturesque topography 

 has been developed. 



This region lies in what is known as the Driftless Area, an area which 

 has not been invaded by any of the great glaciers which covered the 

 state, unless perhaps it was the first, the Nebraskan. Hence not only 

 has the work of the erosive agents been interrupted but the region has 

 not been subjected to the destructive planing action of the great ice sheet. 

 So it is that the unique and beautiful forms resulting from the erosive work 

 of air and water have been preserved under the most favorable circum- 

 stances. In the country immediately to the west, on the other hand, such 

 erosion remnants have been swept away by the repeated advance of the 

 ice, the river valleys have been filled and the resulting topography is a 

 level or gently undulating prairie. 



One of the striking topographic features of northeastern Iowa, one 

 which becomes apparent with a glance at the topgraphic maps of the 

 region and is equally evident to the traveler, is the relatively straight 

 course and smooth, parallel walls of the great gorge of the Mississippi, 

 which is in marked contrast with the intrenched meanders and extremely 

 irregular slopes of the tributary valleys. It is as if some giant plow 

 had been forced down the main valley cutting off all jutting headlands 

 and leaving the valley walls steep and rugged. And this is just what 

 has happened. Great floods of water from the melting Wisconsin gla- 

 cier, ladened with rock, sand and silt, poured down the valley, scoured 

 both floor and walls and then filled the valley to the level of the 

 highest terraces of the present day. The lateral valleys, however, and the 

 back .slopes of the main valley, which were not subjected to this scouring. 

 have retained their older, normal erosion forms. 



There are many beauty spots in this scenic wonderland. Along Oneota 

 river are the great columnar cliffs of Plymouth Rock, the vertical scarps 

 at Bluffton, the ice cave and Mill Spring at Decorah, Elephant Bluff, the 

 Owl's head, Mount Hope and other hills of circumdenudation. The most 

 unique of all these is the Ice Cave. This is a great gap left in the rock 

 by the slipping out of a block of stone along the cliff face. The lime- 

 stones of the region are honeycombed with fissures and into these the 

 cold air of winter is drawn, to be forced out during the warm days of 

 spring and summer. Coming into contact with the moisture laden warm 

 air of the cave this colder air causes a precipitation of the moisture along 

 the inner walls of the cave and forms during the early summer months a 

 coating of ice which sometimes becomes ten to twelve inches thick. Mill 

 Spring is 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 glowing colors of autumn. 



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 



