146- ^y^sconsm Academy of Sciences, Arts^ and Letters. 



the sod covering the ground between the lake and a small lagoon, 

 a distance of about twenty feet, was dislodged throughout the en- 

 tire distance by the force of the ice-shove. (See Plate VIII.) 

 The main ridge which was formed at this place had a height of 

 from three to five feet, but was not as continuous as the one 

 which occurred on Picnic Point. 



This same form of rampart was observed along the shore of 

 Lake Monona. In a number of instances on this lake the ice 

 froze back under the bank and when the ice-shove came large 

 blocks of sod, carrying trees and underbrush, were elevated and 

 displaced. At other places the bank was torn up, forming 

 ridges resembling the one at Picnic Point. East of the assem- 

 bly grounds (See M, Plate I) the sand forming the beach was 

 piled up in a long symmetrical ridge, as shown in Plate IX. 



In several places on Lake Mendota the ice came in contact 

 with small cliffs of sandstone and limestone, and in two of these 

 instances fragments of considerable size were broken off by the 

 ice-shove. 



The third kind of ice rampart has the shape of more or less 

 symmetrical folds, which always occur near the shore, where the 

 water is shallow. As previously stated, the bottom of the lake 

 consisting of mud, marl, moss, and weeds, was frozen in the 

 very shallow places to a considerable depth below the ice. 

 Where the bank was abrupt, the folds were formed out from the 

 shore, but where the shore passed by a gradual slope into marsh- 

 land, the folds were formed on the landward side of the lake. 

 In several places where the lakeward and landward conditions 

 were balanced the folds formed on both sides of the shore line. 

 Where the above conditions prevailed there was formed either 

 a single fold or a series of consecutive folds resembling the Ap- 

 palachian Mountain structure. 



The mxost characteristic and best defined folds of this class oc- 

 curred along the shores of University Bay on Lake Mendota. 

 (See S, Plate I.) The folds at this place were developed on two 

 sides of the bay. The expansion of the ice apparently resolved 

 itself into two components acting approximately at right angles 

 to each other, on account of which the longer axes of the folds 

 on the two sides of the bay were nearly normal to each other. 

 The positions of several of the folds are shown on a small scale 

 in Plate X. 



