280 
DILUVIUM. 
periods, is far better supported by existing facts, 
and is probably that which will eventually be adopt- 
ed by most geologists. Professor Hitchcock, who 
is a close and accurate observer, as well as philo- 
sophical reasoner, concludes, after the most thor- 
ough examination, that " all the diluvium, which 
had previously accumulated by various agencies, 
has been modified by a powerful deluge, sweeping 
from the north and northwest over every part of 
Massachusetts, not excepting its highest mountains ; 
and that, since that period, none but alluvial agencies 
have been operating to change the surface." 
Every part of the United States, and we may say 
the same of northern and middle Europe, if not 
Asia, exhibits abundant evidence of a similar flood 
from the north ; as shown by rocks and bowlders 
being generally found south of the ledges and strata 
from whence they were originally dislodged. 
These bowlders are in some parts of the country 
strewn over the surface in immense quantities, and 
always correspond with the rocks lying north of 
them. They are found on the sides and tops of 
mountains, of a different species of rock from that 
which forms the mountain itself ; and we know of 
no other cause but a powerful flood to explain the 
phenomenon. They are often of great size, fre- 
quently 20, 30, or even 40 feet in diameter, and oc- 
casionally they are so delicately poised upon an- 
other rock as to be easily moved. They are then 
called rocking-stones ; and some, weighing over 100 
tons, can be easily moved by the strength of a single 
man. No one can travel over New- England with- 
out being impressed with a full conviction that, at 
some former period, an immensely powerful current 
of water has swept over the land. 
But it is not to be inferred that the diluvial forma- 
tion is always level, or nearly so ; on the contrary, 
it is often piled up into elevations whose surfaces 
exhibit curves of every description, while the cor- 
