'9°9.] THE CAYUGA LAKE BASIN, N. Y. 373 



During the last half of February and the first of March, 1875, ice 

 thirteen inches thick covered the entire lake. On February 15, 

 1884, the lake again froze over completely and remained so until 

 April 4. Since this date Cayuga has frozen from end to end but 

 once and then during February, 1904. In certain places the ice was 

 22 inches thick. The shallow water at either end of the lake is 

 frozen over usually by the middle of December and remains in 

 this condition until the middle of March or the first of April. 

 Dudley further observes : 



The temperature of the lake unquestionably influences the development 

 of vegetation in its immediate vicinity. Plants on its shores are usually a 

 week later in the spring than in the neighboring ravines and the warm valley 

 about Ithaca, and a week earlier than on the distant hills; and during the 

 first half of November, the blue flowers of Aster Icevis and the white plumes 

 of Aster sagittif alius still remain in considerable abundance, while they have 

 long ago matured and faded near Ithaca. 



Proceeding southward from the gently sloping shores near Cayuga Bridge 

 the banks become gradually bolder, until in the vicinity of Levanna the first 

 cliffs appear on the eastern shore. Between Willets and Kings Ferry these 

 reach their culmination in the " High Cliffs " ; but stretches of lofty, pre- 

 cipitous, or more or less broken declivities occur on both shores until within 

 a few miles of the southern extremity. At intervals, especially near the mouth 

 of some stream, are low, half-sandy points which yield many rare plants. 

 Near Ithaca, and about two miles from the lake, the great valley forks, the 

 main portion continuing to the right of South Hill, a preglacial valley of 

 erosion extending southwardly to Waverly in the Susquehanna Valley. The 

 other portion on the left of South Hill is similar to the first and forms the 

 present Six Mile Creek and White Church Valleys, and opens into the Sus- 

 quehanna at Owego. These deep valleys penetrate and cut through the great 

 dividing ridge between the St. Lawrence or Great Lake hydrographic system 

 to which our streams and smaller lakes are tributary, and the Susquehanna 

 system, and are parallel to similar valleys east and west of us. The head- 

 waters of the streams occupying them, i. e., the summits between the two 

 systems are usually very near the crossing of the dividing ridge. (Dudley.) 



Hydrographic Areas. — A glance at a hydrographic map of the 

 state will reveal the existence of seven river systems, only two of 

 which lie within the province of this paper, namely: the Oswego, of 

 which the Finger Lakes are a part, and the Susquehanna. The 

 latter has in New York a catchment area of 6,267 square miles and 

 comes into very close relation with the Oswego system through 

 the numerous inlets of the Finger Lakes where the origins of many 



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