Knoxville journal. [volume] (Knoxville, Iowa) 1874-1986, 1875-08-19
The Great Ice Sheet.

In the heat OF summer nothing is more
refreshing than generous quantity of ice.
And II may be refreshing to the mind, al
least, TO contemplate in these sultry sum-
mer days the great sheet of ice that once
enveloped all the northern part of our
continent, and of the globe ms well.
All haye seen the immense powders,
called lost rock" in some sections, scat
tered over the northern part of the United
States, which have little or no rescmbiance
to any mass of rock in place anywhere in
their vicinity, and have perhaps asked the
question: Where did they come from
Also the heaps OF sand, gravel, and cob
bie-stones of various sizes which form
many of our ridges, knobs and hills, and
which are totally unlike any fixed rock
near them. Some of these have coarse
and fine pebbles promiscuously mixed to-
gether, and others show beds of stratifi-
cation in which the coarse and fine seem
to be sorted and arranged by themselves
Some, too, have doubtless seen the paral-
lei scratches on the surface of rocks, and
noticed, as the Indians did before them,
that they all have one direction, and that
is usually north and south. Now, all
these phenomena are attributed TO single
SAeSNs anu ttiat 10 Tic SItdi SiiCtt Vi
ice which nature stored up ages
ago without the. necessity of protect
ing il in an ice-house The trans
ported powders, of all sizes down to
pebbles and even fine sand, and the
scratches upon the rocks are clear indica-
tons of movement on very large scale.
And If anyone takes the trouble TO search
for the place whence these erratie powders
came, he will invariably find that it is
north of the position in which they now
rest and varying in distance from few
miles to several hundreds. 1t will very
frequently be found that these masses OF
stone could not have reached their present
resting place without crossing intervening
mountains, valleys, lakes and sometimes
parts of the ocean. They are often perched
in very singular and almost inaccessible
places. There is very large one on the
summit of West Rock, New Haven. under
which the regicides are said to have taken
refuge after the restoration. Some are so
nicely poised In their position that they
can be easily rocked by child, though
they weigh tens of tons. One OF the most
noted of these erratic blocks is called
Pierre Bot. of fine granite, which now
rests on the Jura, 800 feet above Lake
Neutchatel, near the early home of Pref
Agassiz. This has solid content OF
AZ, 600 cubic feet and was transported from
Mont Blanc across Switzerland, distance
of sixty or seventy miles. Through the
influence of their orld-renowned fellow
townsman, the city authorities of Neuf-
chatel have constructed promenade TO it,
To explain the transportation of these
wanderers from their homes, various theo-
ries have been advanced, as the effects OF
Hoods, or of powerful mud currents, gas
explosions of great Violence, hurting rocks
in all directions, and drifting ice, carrying
powders on its mass and depositing them
wherever the ice melted But these and
many others fail 10 satisfy the observed
conditions, and utterly fall to the ground
in presence of the facts. To our lamented
AgassiZ belongs the credit Of first attribut-
ing the cause of all our drift phenomena
to glacial action. But he was not the first
10 observe that powders were carried
long distances by land ice. More than
twenty years before Agassiz announced
his conclusions, chamois- hunter of Va
lais said TO M. Charpentier: "Our glaciers
had formerly much longer extent than
al present. Our whole valley was ocCu
pied by vast glacier, extending as far a.
Martigny, as is proved by the powders
found in the vicinity of this town, and
which are far too large for the water e.
have carried them thither" Charpentiei
adds that he afterward received similar
explanations from mountaineers in other
parts of Switzerland; once, in 1884, from
woodman, when he had, at the very
time, in his pocket, Il paper advancing
lac (which lac. IhDY, ,yyxif,
10 Lucerne to submit 10 convention OF
Swiss naturalists.
In 1886 Agassiz became acquainted
with Charpenter, and was made familiar
with his investigations. Soon after he
(Agassiz) carried the theory beyond the
limits of the Swiss Alps, and made 1t en-
brace a sheet of snow and ice extended
enough TO cover a continent. Having no
ticed that the markings in the region OF
the Alps below the glaciers were the same
as those found beneath the ice mass, he
compared these with similar appearances
in Northern Europe and Asia, which were
generally attributed 10 the great flood, and
made the bold generalization that all were
due to the very same cause, and that one
vast sheet Of ice must have covered all the
northern regions of the globe. While
these theories at first met with great opp0-
siti"n, they are now universally accepted.
According to Agassiz, the sheet Of ice
extended in this country as far south as
South Carolina or Alabama, and was
thick enough to cover all the mountains
of the eastern part Of North America with
the exception of Mount Washington. This
peak projected, lone sentinel on that
vast waste OF ice, 200 or 800 feet In the
latitude of Northern Massachusetts, he con-
ceives the ice to have been between two
and three miles thick; and IL held its d.
rect southerly course In spite of the mount
aims and ridges over which IL moved, as
is indicated by the direction of the paral-
lei grooves IL made, and the trains Of
powders which it left. The powders
were all torn off by the advancing ice
sheet from the projecting rocks over which
ii moved and carried or pushed as . bot
tom drift, scratching and blowing the sur
face over which they passed, and being
scratched and polished themselves in re.
turn, till they were finally brought 10 rest
by the melting of the ice. They were not
carried as far south as the ice sheet ex.
tended, seldom beyond the parallel of 40
deg. north. The native copper of Lake
Superior was drilled 400 or 500 miles
south, and tie pudding-stones OF Roxbury
Mass, were carried rs far south as the
island of Penikese