THE PELHAM LAKE AND ESKER. 579 



down into the basin toward the east in a series of Ijeautiful terraces, and 

 on the opposite side descend in a series of terrace scarps and irreguhir 

 slopes to the level of tlie normal high terrace of the Connecticut River, 

 at 290 to 295 feet. Looking across to the northern horizon, one sees two 

 slight, broad depressions in the line which joins the eastern and western 

 bounding ridges — by Avhich the two roads pass north from Pelham to 

 Shutesbury — and these mark the southern termini of two valleys by which 

 the waters which deposited the sands entered the basin. Their elevation 

 at the southern end, where they open into the basin and whence the terrace 

 sands extend southwardly, is 820 feet above sea, and they run tar north, 

 rising slowly and showing abundant traces of the passage of the waters 

 in their shape and in the tails of sand which lie in the lee of projecting 

 rocks. 



But the most remarkable deposit of all is a great ridge (k) of yellow 

 sand (see PI. XIII), 40 to 50 feet high, which starts from the mouth of the 

 eastern of these channels and stretches down the slope of the basin south- 

 ward with sinuous course, bending at last westward and skirting the brook 

 and running for a long distance out upon the till of the valley bottom, from 

 which it is as sharply demarcated as a new railway embankment thrown 

 across a grassy field. This ridge has sharp slopes on either side, and ends 

 abi-uptly far in advance of the remaining terrace sands. Much of it is a 

 rather coarse sand, or rather a sand with many pebbles, and rarely a great 

 bowlder is embedded in it. It di'ops by great steps, so that one is at first 

 uncertain whether to consider it an esker in the sense now current, or to 

 think it a section of the ordinary teiTace sands, from which streams cutting 

 back into the mass on either side — their waters being held up to the sand 

 level by the subjacent till — have removed so much of the loose material 

 that this long ridge remains as an index of the former greater extension of 

 the sands toward the center of the valley. 



The entire freedom of the broad bottom of the basin from sand or 

 clay, and the great improbability that any such deposit has ever been 

 present and been so entirely removed that no trace or indication of its 

 presence or of any erosion by which it can have been removed is discern- 

 ible, make it far more probable that the first explanation is the true one, 

 and that it is a deposit in a temporary ice channel, di'opped by the melting 

 of the ice on the steep slope down which it now winds like a great snake. . 



