66 NEW YORK STATE MUSEUM 



Northville are located. During the general ice retreat, but Avhen the 

 Mohawk valley lobe of ice was still present, morainic deposits 

 accumulated along the ice margin across the mouth of the valley 

 thus ponding the waters over the valley bottom and causing the 

 Sacandaga river to find an outlet over the low divide at Conkling- 

 ville. Perfect delta sand plains may now be seen at approximately 

 780 feet above sea level. This lake persisted for a good while after 

 the disappearance of the ice because of the effective morainic dam, 

 and even today in the spring of the year a wide swamp becomes 

 flooded. The lake was drained by cutting down the' outlet at Conk- 

 lingville. Construction of the proposed Sacandaga reservoir, by 

 means of a dam at Conklingville, would almost exactly restore this 

 former glacial lake. 



Great terraces and sand fiats show the form'er existence of a large 

 body of water in the valley around Corinth (Saratoga county), and 

 another in the vicinity of Warrensburg (Warren county). 



The former extensive lake, called Glacial Lake Pottersville, of 

 which Schroon, Brant and Paradox lakes are remnants, has already 

 been described. Numerous excellent delta sand flats mark the old 

 lake level. Construction of the Schroon lake reservoir, as proposed 

 by the State, would almost exactly restore this great lake. 



A well-defined glacial lake filled the bottom of the valley at Wells 

 (Hamilton county). 



In the northeastern Adirondacks there were, according to Mr H. 

 L. Ailing, several extensive high-water lakes, the principal ones 

 having been in the Saranac lakes valley with water levels ranging 

 from 1600 to 1450 feet (present altitudes) ; in the broad valley south 

 and southeast of Lake Placid with water levels from 1875 to 1800 

 feet ; and in the broad valley around Wilmington with waters at from 

 1 1 50 to 1 100 feet. 



The above-described extinct lakes are only some of the more 

 important ones which have been studied in the Adirondack region. 



Drainage changes due to glaciation. Drainage changes due to 

 the Ice Age are common in the Adirondacks, though many of these 

 have not yet been worked out in detail. Some of the more promi- 

 nent changes which have been studied will be briefly described. As 

 a result of long preglacial erosion, it is certain that deep, narrow 

 gorges and waterfalls must have been very rare if present at all. 

 Like lakes, such features are ephemeral because, under our con- 

 ditions of climate, gorges soon (geologically) widen at the top, and 

 waterfalls disappear by retreat or by wearing away the hard rock 

 over which they fall. 



