256 Address before the Association of American Geologists. 
hundred feet below their tops, and pass over them without los- 
ing their parallelism; and yet the situation of the drift shows 
that these markings were made by an ascending and not.a de- 
scending body. Such might be the effect, if the whole surface _ 
of the country were covered “4 a thick sheet of ice irs . 
a southerly direction. 
Of the. other case, I have met with two examples in- New 
England, and know not that they have been noticed elsewhere. 
In these cases, the perpendicular layers of argillaceous: and horn- 
blende slate, covered in one place, by fifteen or twenty feet ‘of 
drift, have been fractured to the depth of ten to fifteen feet, soas 
- to be more or less separated, producing horizontal fissures, whieh 
are filled by mud, while the laminzare inclined, at: various angles: 
In short, it seems as if an almost incredible force had been exet- 
ted upon the surface in an oblique direction. Such a force. might 
be exerted by an immense mass of ice in the process of expan~ 
sion ; but I know of no other source from which: it ieee have 
been derived.* © tire 
On the other hand, there are fentines in Ne ihenoenet of di 
luvial action in this country, which are explained by this theory 
in a much less satisfactory manner. One is the southerly di 
tion which our drift has taken, and the great distance to’which tt 
has been carried. Tt cannot be conceived that’ any single glaciet 
‘ole NS 
PHUUUMLU LiadVO 
tion, especially « over a sited which could have had scarcely any 
southerly slope. Even if we admit a Mer de Glace in:the north 
-ermregions so lofty as, in the beginning of the work, to send gla 
ciers a vast distance, yet the force seems to have continued: to 
operate in the same austral direction, even to the bortomalt™ 
valleys. It is, however, probably true, that the great mass” 
drift will be Saat within fifteen or twenty miles from i 
Place ; and that which occurs at greater distances, may Hd 
have been transported by powerful currents of water. risa 
most certain that the sheet of ice which covered the sige 
agi ose peearapisa 
“aletpn Wb shor 2 de cach ce gram nth ramp 
«Dative ad sch th ca he od 
