310 J. F. Kemp — Buried Channels Beneath 



ward is the present Rondout Creek, now flowing on drift at 

 the line of the section. A little to the north, however, it 

 swerves eastward and cascades over a ledge of Manlius lime- 

 stone. About 400 ft. west of the point where the siphon 

 passes below the present stream, the drill revealed an old, 

 buried channel with a bottom at minus 10, or beneath some- 

 what over 200 ft. of drift. The pre-Glacial stream had 

 evidently followed down a dip slope of Manlins, sapping the 

 edges of the Coeymans (labeled C in the figure) and New 

 Scotland limestones until it also was obliterated by the drift. 

 We think it had left a projecting ledge of Manlius as shown 

 in the figure, because the drill passed from drift into limestone 

 and then into drift again before it caught the bed-rock. The 

 Manlius is the formation containing the waterlime beds, and 

 its subdivision into the Rondout, Cobleskill, Rosendale and 

 Manlius proper has not been attempted here. Somewhat con- 

 trary to one's natural expectations, it (an argillaceous variety) 

 is the formation containing the fissures and caves of the 

 region, whereas one would be inclined to look for these rather 

 in the Becraft, which is a very pure limestone. The ancient 

 Rondout Creek moreover, somewhat strangely, seems to have 

 followed the Manlius rather than the hard Shawangunk grit 

 with its soft overlying High Falls shales, which were cut far- 

 ther east. 



Of the further relations of this buried channel we have no 

 records. The Hurley crossing showed a depth of minus 68, so 

 that so far as gradient is concerned it might have gone out 

 this way. 



A mile and a quarter eastward there is a patch of drift in a 

 little synclinal valley of High Falls shale, whose bottom stands 

 at 160 plus, but the depression is of no great consequence. 



The Wallkill Crossings.— After passing through the Sha- 

 wangunk ridge by a tunnel at grade, the aqueduct turns south- 

 west along the surface and crosses the Wallkill valley near the 

 little hamlet of Libertyville, three miles southwest of New 

 Paltz. The. entire tunnel will be in Hudson River slates. 

 Before this line was selected, however, two lines of borings 

 were made near Springtown about three miles north of New 

 Paltz and several additional ones in or near the town, which 

 are not here used, as they introduce no essential change in the 

 conclusions. The two Springtown lines are rather less than a 

 mile apart and are called, on fig. 5, Springtown A and Spring- 

 town B. In the former a buried channel was found at minus 

 79 almost beneath the present river, which stands at plus 150 

 or about 229 feet above. The old channel is filled with drift. 

 About a half mile westward a small depression was detected at 

 plus 50, evidently marking a tributary and smaller stream, 

 separated by a divide of less than 40 ft. 



