412 » W. M. Davis—Origin of Drumlins. 
1815, vii, 169). After describing the general form and _ struc- 
ture of those about Edinboro’, he says: “The facts seem to- 
meet the challenge held out by Mr. Playfair in the following 
passage from his Illustrations of the Huttonian theory, art. 366. 
‘If there were anywhere a hill, or any large mass composed of 
broken and shapeless stones, thrown together like rubbish, and 
neither worked into gravel, nor disposed with any regularity, 
we must ascribe it to some other cause than the ordinary detri- 
tus and wasting away of the land. This however has never 
yet occurred, and it seems best to wait till the phenomenon is 
observed before we seek for the explanation of it.’ Now it 
appears to me, that these vast assemblages, in which blocks of 
every size, and shape, and quality, some sharp, some round, 
are confusedly scattered through clay, are inexplicable by any 
diurnal cause, and do call for some particular solution” (p. 174). 
Sir James consequently decided in favor of earthquake waves - 
as a means of forming drumlins: he recognized that the 
ridges of compact clay were parallel to one another (p. 177), 
to the scratches on the bed rock below (p. 183), and con- 
sidered vast diluvial waves competent to produce all these~ 
effects. . Others of the older geologists have since then ascribed 
drumlins to the rush of diluvial floods; but it is noteworthy 
that no explanation of drumlins by iceberg action has yet 
been suggested. These hills indeed offer strong evidence 
against the sufficiency of that theory. 
t is unnecessary here to enter on the evidence that places 
unstratified drift, with its scratched stones and large subangular 
owlders, among the effects of land-ice action. Since it has 
been generally thus regarded, several suggestions of more detail 
have been made as to the origin of the peculiar form of drum- 
lins. They have been considered the product of post-glacial 
erosion acting on a broad sheet of drift by W. Harte (Journ. 
Roy. Geol. Soc. Ireland, 1867, ii, 30) and Professor Shaler, 
(1. ¢.), but this explanation does not account for the remarkable 
scattered, with numerous and wide spaces between them oceu- 
pied by insignificant deposits of till, the suggestion is not so~ 
