394 The American Geologist. June, isw 
Hitchcock- and Wrightf and held by some others. This sug- 
gests that a re-advance of the ice modified the terminal mo- 
raine deposits into drumlinoid forms. This theory seems to 
be generally abandoned, and apparently Wright, in one of his 
later publications, J is inclined to accept the next theory as 
more probable. It is this theory, however, which the author 
now brings forward again. 
The hypothesis at present most currently accepted was first 
suggested by Kinahan and ( 'losejj to account for the drumlins 
of Ireland, and is also advocated by Geikie|| in England, and 
by Davis.** Chamberlinf f, Salisbury, + + and others, in America. 
This theory considers these hills to be of constructional rather 
than destructional origin. That is to say, by variations in 
current or drift-supply the ice is supposed to deposit more 
material at one point than at another and to produce the 
drumlins by successive additions, in a manner comparable 
with the formation of a sand bar in a river. Professor Cham- 
berfin,§§ and indeed others as well, has assumed the probable 
existence of a rock nucleus: but it is hardly probable that, 
in the light of later studies, these authors would now advo- 
cate this view. 
A.S has been said. Wright at present advocates this theory: 
and originally Upham || || also believed this to be the origin of 
drumlins. At present, with the exceptions of Shaler, Hitch- 
cock, and Upham, there are, so far as I am able to ascertain. 
no American glacialists, who have expressed themselves on the 
subject, who do not accept this theory as at least the most 
probable: and some apparently consider it proven. 
*Pjroc. Boston Soc. Nat. Hist.. 1876, vol. xix, pp. 63-67. 
fProc. Boston Soc. Nat. Hist.. 1876, vol. xix, p. 58; 1879, vol. xx, p. 217; 
The Ice Age in North America. Third Ed., 1891, pp. 259-260. 
+ Man and the Glacial Period, 1893, p. ;.">. 
gGeneral Glaciation of lar-Connaught. Dublin. 1872. 
[The Greal tee Age, 1874, pp. 88, 97. 
**p r oc. Boston Soc. Xat. Hist.. 1882, vol. xxn. p. 41: Am. Jour n. Sci., 
third series, LSS4. vol. xxvm. p. 415; Science. 18S4. vol. iv. p. 120. 
(•fGeology of Wisconsin, 1873, vol. i. p. 283; Third Annual Report, U. 
S. ( ieol. Survey, p. H06. 
$£New Jersey Geol. Survey, Annual Report lor 1891, pp. r 1 - 7 -~> . 
§§Third Annual Report. I'. S. (ieol. Survey, p. 306. 
((Geology of New Hampshire, vol. in. p. 308; Proc. Boston Soc. Nat. 
Hist.. 1879, vol. xx. p. 2'Xi. and also in later volumes. 
