148 Bulletin Wisconsin Natural History Society. [Vol. 8, No. 3. 



regular watercourse has been formed, rivuline is added to the 

 pluvial erosion, deepening and later on widening the ravine, giving 

 rise to branch ravines, and often forming a complicated river sys- 

 tem in miniature. Most of these ravines cut back into the high- 

 land for less than a quarter of a mile. But a few have a different 

 origin and consequently a larger extent. These, like that of Oak 

 Creek in South Milwaukee, are formed by some brook taking its 

 origin in one of the many swampy depressions far inland and 

 meandering sluggishly about as a peaceful meadow stream, doing 

 very little erosive work, till it strikes the edge of the plateau. Then 

 it cuts rapidly through the bank, till it has formed a winding 

 canyon more than a mile in length. 



The erosion terraces mentioned above are of far less extent 

 than others which we may distinguish as diastrophic, without pre- 

 judging their origin. 2 These are a feature of Lake Shore topo- 

 graphy for a long distance northward. Two are included in the 

 present area : One in Lake Park ; the other, larger one, at Fox 

 Point. They are practically level, from five to forty rods wide, 

 and raised some fifteen feet above low water mark, while their 

 landward side is bounded by the continuation of the shore cliff. 



B. Local Climate. 



The local climate of the area is evidently quite different from 

 that of the uplands, although exact data on this point are lacking, 

 no accurate and long-continued observations having been made. 

 The principal differences seem to be greater average moisture of 

 the atmosphere, and slightly less extreme temperatures. 



The number of foggy days, when the atmosphere is saturated 

 and transpiration of plants much depressed or suspended, is much 

 greater along the shore. It is not uncommon to see the fog rise 

 precisely to the top of the bank, filling the ravines, but not visible 

 anywhere on the uplands. The dry northwest winds, which are 

 very prevalent in the region, are quite ineffective under the lee 

 of the bank. Sometimes, while a strong; wind is blowing above, 

 not a breath stirs a few feet below the edge. On the other hand, 

 the shore region is exposed to the full force of the cool, but com- 

 paratively moist easterly winds, which prevail especially during 



2) They were quite evidently part of the floor of the Lake, when the 

 water stood at a much higher level than now, and are possibly correlated in 

 time to the rivi r t Traces in the Menomonee Valley. 



