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Proceedings of the Royal Society 
speculations of Agassiz, that a gigantic glacier formerly existed, 
emanating from the North Polar regions, and flowing over the 
whole northern hemisphere. 
The author said he did not adopt this view. He held that the 
boulder-clay was not a land deposit, but one which had been 
formed at the bottom of the sea ; that it originally consisted of 
the ordinary beds of mud, sand, gravel, or boulders, such as are 
found generally at a sea-bottom ; and that these beds were in- 
vaded by icebergs, which ploughed them up, and mingled them 
all together, so as to produce what is called boulder-clay. His 
reasons for thinking so were these — 
1. True boulder-clay is not found in Switzerland, though, if its 
formation is due to the action of glaciers, it ought to be found 
there. 
2. Boulder-clay is found in many places where it is not con- 
ceivable any glacier could have existed, or, at all events, have had 
any connection with the deposit. 
3. An examination of the materials composing the boulder-clay 
showed that these materials had been in motion ; and as it appeared 
that the motion was everywhere from the same direction, viz., 
from the west or north-west, it was impossible to explain such a uni- 
formity of direction, extending over so large an area, without sup- 
posing that there had been a great oceanic current, which operated 
in producing that motion. 
4. The circumstance, that almost everywhere, boulder-clay is asso- 
ciated with marine Pleistocene strata, and that in very many places 
in Scotland, Ireland, and England it contains marine fauna, is a 
strong proof that it has been formed at the bottom of the sea. 
5. The boulder-clay shows, however, from the absence of strati- 
fication, from the broken state of the sea shells, and from the un- 
natural mixture in it of littoral and deep-water shells, that some 
agent has operated on it, causing great disturbance, and acting 
with immense mechanical power. 
6. The accounts given by voyagers to the arctic regions, show 
that icebergs there disturb the sea-bottom, and produce operations 
very analogous to those which are inferred to have occurred in the 
production of the boulder-clay. 
7. The character of the shells in the boulder-clay, and in other 
