FIRST STAGE OF THE GLACIAL LAKES. 433 



in general an east-and-west line. As a matter of fact, the highest water- 

 planes do so correlate with the theoretical outlets. 



Description of the glacial Lakes. 

 first stage: three primary lakes. 



Outlets. — Their outlets were by the headwaters cols. 



A glance at the map will show that the Genesee river originates in 

 Potter county, Pennsylvania, in three subequal, northward -flowing 

 streams, known as the east, middle and west branches, which unite near 

 the village of Genesee (formerly called Genesee Forks). These streams 

 lie in comparatively deep valleys, carved out of the high tableland, the 

 intervening ridges being higher than the headwater cols. The writer 

 has not visited the sources of these three streams, and his information 

 concerning the divides is obtained from other persons, and particularly 

 from Professor N. S. Shaler, who has kindly loaned some unpublished 

 notes of a visit made a few years since to those headwaters. 



The streams are described as heading in swamp cols, but with no con- 

 spicuous or strong channels or scourways leading southward from the 

 divides. 



Life history. — As the high land about the sources of these streams was 

 uncovered by the ice the glacial waters were at first ponded in many 

 lakelets and escaped by numerous outlets. Later, by a further retreat 

 of the ice, these lakelets were drained or blended, until, theoretically, 

 there was an episode during which a lake existed in the valley of each 

 of the three branches of the Genesee. These were not very important in 

 any respect, but, to make a complete history, must be considered. The 

 lake phenomena and outlet channels should, theoretically, not be well 

 developed for the following reasons : 



(1) The life of these separate lakes was very short, as a few miles 

 further retreat of the ice-front inaugurated the next stage of the glacial 

 waters. (2) The surface of the lakes was probably very fluctuating. (3) 

 Each valley caught the drainage of only a very limited portion of the 

 ice-front. If the ice-front was generally east and west, then the drainage 

 both east and west of the narrow Genesee basin drained directly in south- 

 flowing streams (see map) ; but if the basin was occupied bj^an ice-lobe, 

 the waters from the sides of the lobe further north found lower outlets. 

 (4) The ice-front was perhaps comparatively thin and supplied for the 

 area a small amount of water. The district is close to the limit of the 

 glaciated area; indeed, the west and middle branches of the Genesee 

 have their sources in the great terminal moraine.'^ 



* Second Geol. Survey of Penaa. Report Z, Terminal Moraine, pp. 141-143 and moraine plate vi. 



