158 



SCIENCE. 



[Vol. VIII^ No. 185 



tail ; 6°, pre- crag and combings ; and 7°, veneered 

 hills. The most remarkable are the mammillary, 

 lenticular, and elongated ridges, frequently 

 grouped under the term ' drumlins.' The lentic- 

 ular varieties prevail in southern New Hampshire, 

 central and eastern Massachusetts, north-eastern 

 Connecticut, and Nova Scotia ; the elongated va- 

 riety, accompanied by shorter, in central New 

 York ; and all varieties in eastern Wisconsin, ex- 

 tending into the northern peninsula of Michigan. 

 About three thousand have been mapped. The 

 total known number probably aggregates ten 

 thousand. No theory of their formation has yet 

 received wide acceptance, beyond a general agree- 

 ment that they are subglacial accumulations. 



Turning to the assorted drift, two classes com- 

 monly embraced there were excluded. First, the 

 ' orange sands ' of the Mississippi vaUey, com- 

 monly accepted as Champlain deposits. They do 

 not appear to possess the distinctive character- 

 istics of glacial gravels, but are residuary in aspect. 

 If they belong to the glacial period at all, it must 

 be to its earliest stage. Their reference to the 

 Champlain epoch is clearly an error. The second 

 class, set aside as not being strictly glacial, were 

 those reworked by wholly non-glacial agencies ; 

 or, in other words, the secondary drifts. Elimi- 

 nating these, there remain the products of glacial 

 waters working co-ordinately with the ice, of 

 which two classes were recognized : 1'', those that 

 gathered immediately within and beneath the ice 

 body itself, or against its margin ; and 2°, tliose 

 which were borne to distances beyond its limit by 

 the glacial drainage or by peripheral waters. In 

 the first, the presence and restraint of the ice w^as 

 an essential factor ; in the second, it was only a 

 source of material. Of the first class, there are : 

 P, the products of streams flowing on the surface 

 of the ice ; 2°, of streams plunging from the sur- 

 face to the base through crevasses ; 3°, of sub- 

 glacial streams in tunnels beneath the ice ; 4^*, of 

 streams in ice canons at the border ; and 5°, de- 

 bouchure deposits of streams at the margin. The 

 products embrace a great vai'iety of sub-types of 

 gravel heapings, including isolated mounds, coni- 

 cal peaks, clustered hummocks with inclosed pits 

 and basins, and sharp, steep-sided ridges, often of 

 phenomenal length — all possessing great irregu- 

 larities of material and stratification, embracing, 

 frequently, manifest disturbances. The elongated 

 variety, — identical in all essential respects with 

 the great osars of Sweden, — are finely developed 

 in eastern New England, especially in Maine, and 

 the border of New Brunswick ; while the hum- 

 mocky variety, constituting the ill-defined class of 

 kames, are abundant throughout New England, 

 New York, northern New Jersey, Pennsylvania, 



Ohio, Indiana, the greater part of Michigan, 

 northern Illinois, eastern and northern Wisconsin, 

 northern Minnesota, north- central Iowa, eastern 

 Dakota, and many portions of Canada. These 

 osars and kames are among the most fascinating 

 phenomena of the drift ; but to differentiate them,, 

 and to determine to what extent they are super- 

 glacial, subglacial, and debouchure phenomena, is 

 a triumph of discrimination not yet attained. It 

 is of most practical importance at present to dis- 

 tinguish debouchiu-e and submarginal gravel heap- 

 ings, representative of the position of the glacier's 

 edge, from the gravel veins of the glacier's body. 

 The semi-morainic kames are the type of the one ; 

 the winding windrows of gravel, the osars, of the 

 other. The osars frequently end in osar fans,, and 

 the kames graduate into pitted gravel plains. 

 These pitted plains and others, not identical in 

 type, constitute one of the singular and not least 

 puzzling features of the assorted drift. Thej 

 have a wide range ; but find their most phenomi- 

 nal development in Wisconsin, Michigan, Ontario,, 

 and the coast of New England. The kames also 

 graduate into true moraines ; and every stage of 

 gradation may be observed. In the progress of 

 their accumulation, they were thrust by the ad- 

 jacent ice, and heaped into ridges as genuinely 

 morainic as though made of unwashed material. 

 They have an especial development along the in- 

 ter lobate tracts. 



Of valley drift formed by streams heading on 

 the glaciers, tlie intermediate phases were passed 

 with simple reference, and attention directed to 

 two extreme phases: 1°, the moraine-headed val- 

 ley trains ; and 2°, the loess tracts. The former 

 are deposits of glacial floods, when the slope gave 

 impetus to the drainage ; the latter were construed 

 as the px-oducts of slack drainage. The former are 

 found to show progressively coarser material 

 toward their origin, and to merge into elevated 

 expanded heads blending with the moraines from 

 which they took their origin. Associated with 

 these are glacial aprons of overwash drift, that 

 fringe the outer sides of moraines in favorable 

 situations. These phenomena point unequivocally 

 to a glacial origin, and to vigorous drainage con- 

 ditions. Contrasted with them are the broad 

 tracts of fine silt, designated ' loess,' that occupy 

 the Mississippi up to east-central Minnesota, the 

 Missouri up to southern Dakota, the Illinois and 

 Wabash as far up as their great bends, and the 

 Ohio up to south-eastern Indiana. They are so 

 correlated with the border of the ice, in the later 

 stages of the earlier epoch, that they seem clearly 

 to be products of glacial drainage of a fluvio-lacus- 

 trine character, indicating low gradients and slack 

 drainage. This stands in marked contrast to the 



