26o The American Geologist. October, 1902. 
of three thousand miles, and forms one of the most extensive 
moraines in the world. 
The older drift formation, or series of formations, than the 
moraine above cited, is in evidence at its easternmost point in 
southwestern Ohio, and reaches its southernmost limit near the 
junction of the Mississip])i and Ohio rivers. Thence it contin- 
ues northwestward followmg^ approximately the course of the 
Missouri river, and always passing- under the more recent for- 
mation on the north. It is noticeable moreover, that the south- 
ern border of this drift area in both the earlier and later forma- 
tions, presents a distinctly lobate appearance, the earlier stages 
being- less pronounced than the later.* 
A form of glacial prominence which is often associated with 
terminal moraine formations is known as drums, or drumlins. 
These most frequently consist of unassorted drift, though some 
are shown to be composed chiefly of boulder-clay ; in some 
cases they are stratified near the base, and not a few, as pointed 
out by professor Shaler, have nuclei of solid rock. The typical 
form is lenticular, grading into elongated or elliptical moimds 
whose major axes extend in the direction of movement of the 
ice sheet. The origin of these forms does not appear to be 
perfectly comprehended, though in a general way they are 
classed as ground moraine formations. 
A famous locality for drumlins is New England, where in 
Boston harbor, and neighboring parts of Massachusetts the tvp- 
ical lenticular form is well exhibited. They occur also in New 
York between Batavia and Rochester, and between Lockport 
and Niagara falls. The most extensive drumlin area, however, 
is probably that of eastern Wisconsin, which has been estimated 
by Buell to contain 10.000 drumlins. "AH these tracts of pro- 
nounced drumlins," says Chamberlin, "lie north of the chief 
belt of terminal moraines and evidently belong to the later glac- 
iation." 
Geikie says of the drumlins of Scotland, "In the central 
portion of a broad Lowland valley, where superficial accumula- 
tions are thickest, the drums are invariably composed of boul- 
der-clay alone. Toward the sides of the valley, however, where 
the till is thinner, the 'drums' occasionally show a core or nu- 
*M£ip of the Glacial Striae of the Eastern I'nited States — Rock Scor- 
ingrs of the Great lee Invasions. 7th Ann. Rept. of U. S. Geol. Sui-^-ey. 
1888. 
