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THE AMERICAN NATURALIST [Vol. XLI 



In a very large number of cases examined the stones were found 

 to be piled quite loosely so that the slightest jar set them sliding 

 down into a position of more stable equlibrium. 



Along the larger streams and rivers the heaps are usually found 

 in small bays off the main stream or on bars and ridges on the 

 sides of the main channel, in quiet but never in dead water. In 

 some places near the watersheds they occur in midstream, and 

 occasionally they are sufficiently numerous to hinder and partly 

 obstruct canoe navigation, where the water is shallow and th^ 



Fig. 1. 



In the early spring when the waters are high and usually more 

 or less turbid the cones are not in sight; but as the waters recede 

 the apices of the cones gradually appear above the surface and 

 late in the season the water may have receded so that the whole 

 cone together with the bar on which it was built comes into view. 

 The tops of the "nests" shown in figures 2 and 3 were fully five 

 feet above the surface of the water when the pictures were taken 

 in August. In early June the water was probably six feet higher 

 and the tops would have been under at least a foot of water. 



As to the origin of these curious heaps of pebbles, the Indians 



