10 PROCEEDINGS OP BROOKLYN MEETING. 



along the very summit axis, beginning sometimes far below the summit on the 

 north end, cutting through the highest part on its way and continuing down the 

 south slope to the base of the hill, its bed having a continuous southward slope 

 from its first starting point. In a few cases, as at the hill south of Whittier's 

 birthplace, in Haverhill, the channel passes along one side of the hill for some dis- 

 tance, then suddenly cuts transversely across its axis, and then passes southward 

 along the opposite side. Some of the complex drumlins have a ridge-like form 

 extending east and west or nearly so— sometimes divided on the summit by very 

 shallow incipient valleys into separate summits —sometimes presenting no trace of 

 such divisions. The erosion channels found on them may commence south of the 

 east and west axis and slope down the south side, or they may begin on the north 

 side one-half or more of the way up, cut through the axis and down the south side 

 with a continuous south slope of the bed from its first appearance. The southward 

 slope of the bed of the channel throughout its entire length is a marked charac- 

 teristic, as it is very exceptional to find the northern portion of the bed sloping 

 northward, though such cases do occur, as at Brown hill, east of Ayer Junction, 

 and at North Leominster. 



The same rule holds with the smaller channels, which, with rare exceptions, are 

 found entirely upon the south slopes or on the southeast or southwest sides. 



As an example for more detailed consideration, I have selected a drumlin having 

 nearly the perfect tj^pical form, which has a channehof moderate size nearly coin- 

 cident with its longer axis for almost its entire length. This hill is situated in that 

 part of the town of Stow known as Rockbottom, a region where drumlins are 

 fairly numerous, there being from twenty-five to thirty within a radius of five 

 miles. The Assabet river fiows through this group, winding in curves of a mile or 

 more in radius, but nowhere cutting into any portion of them nor having ever 

 exerted an erosive power upon them. Directly north of the hill selected for de- 

 tailed study and just across the river are two hills of the same elevation it has. 

 One of them is a typical drumlin ; the other an irregular mass of till. Within a 

 third of a mile to the northeast and east, there are two more of similar character. 



Southward about a quarter of a mile is a broad, flat mass of till, over which passes 

 an esker, of which more will be said. Immediately to the west or slightly south- 

 west is a nearly typical drumlin so closely connected with the one under discussion 

 that the valley between the two is elevated one-half the height of the hills above 

 the general level of the country. 



The altitude of the bottom lands along the course of the river is 200 feet above 

 sea-level, and above them the hill given on the map as Orchard hill, but known 

 locally as Gleason's hill, rises about 100 feet, making its altitude above the sea 300 

 feet. It has a length of about half a mile and a width about one-half as great. 

 As seen at a little distance from the east, it presents the smooth, graceful outlines 

 of the ordinary type, except that it has a long, gentle slope to the south and a much 

 steeper one to the north. 



Ascending the type drumlin from the east to the line of the axial summit, a deep 

 channel is found, which, from its winding, tortuous form, conveys the impression 

 that it is a deserted water-course. Beginning at the north end of the hill, at an 

 elevationn of about three-fourths its height, or 75 feet, it passes directly along the 

 axis down the south slope, a distance of 2,000 or more feet, to the base. The bed 

 has a southward slope throughout its entire course, except for a few feet at the 

 north end, where the slope is northward. The greatest depth of the channel, 27 



