141 



black imid arc in the progress of formation. The waves throw up the mud 

 In the form of loops and bands, and so form small irregularities in the 

 coast line. An examination of the mud thrown up or built up in these 

 situations shows it to be composed of small pieces of Scirpus in various 

 stages of decay. Thus the Scirpiis furnishes a large amount of material 

 for the building up of new shores. Besides the comminuted and decayed 

 tScirpus there are occasional banks of broken »s'cirp»s stems, not yet de- 

 cayed nor much broken up. piled like windrows up beyond the summer 

 water line. These banlcs are probably piled up during the high water 

 of spring or shoved up by the ice. Upon the soft, black mud banks men- 

 tioned above, tliere springs a dense growth of amiual weeds which forms 

 the advance guard of land vegetation in these regions. 



It may be tliat the lake plain lias for its foimdation decayed tScirpiis 

 stems, to which is added turf from the sedges that today so tliickly clothe 

 its surface. 



As has been said, long stretches of shore are made up of a tirm. whitish 

 sand. Such stretclies are to be fotmd along the Assembly grounds, north 

 of Chicago Hill pier, and in the vicinity of the mouth of Clear Creek. Tliis 

 sand is often fotmd floating in lilnis on the surface of the water near 

 shore. At the mouths of the creeks, banks or deltas of white sand are 

 built up and these project above the sttrface of the water Avhen the lake 

 is low. and form islands. At other places it can not l)e said definitely that 

 either erosion or sedimentation is taking place. Gently lapping waves will 

 pile up a narrow ridge of sand just at the edge of the water. Imt high, 

 strong waves will wash them down again. During active wave motion the 

 advance of the waves will move particles of sand shoreward, while tlie 

 back flow will move them back about the same distance. 



Freciuently on the sandy banks, perhaps everywhere in stich places 

 Avhere not interfered with, tlie three-cornered rush Srii-jms (iiiici-inoiiis, 

 grows out and forms the advance guard of vegetation. 



THE FLORA OF THE LAKE SHORE is not essentially different in 

 species from that of the shallow ponds adjacent to the lake, especially the 

 large pond on the southern shore. Tlie only difference is that the plants 

 in that pond (bulrush, cat-tail, spatterdock. pickerel-weed and arrowhead) 

 form large patches, as they have here a l>r()a(l region of shallow water and 

 congenial soil. Along the lake shore the plants, all except the bulrush, 

 form comparatively narrow belts. :\[ost of the bulrushes {ticirpiis laeustris) 

 in the ponds outside of the lake are light in color and soft in texture (there 

 9— Academy of Science. 



