New-York tribune., 1842-01-17
Reported for the Ne"-Ysrk Tribune
Prof. Sillimap'S Second Lecture.

I
Professor SIL11NAS in introducing his seceRd
lecture Oh Geology, said that the subject seemed
10 grow before his ow4 mind, and that It was Ut
terly Impossible to DO any justice within SO Die,
compass. He apolegised tor the desuitofy aiu
disconnected manner in which the prominent 'acss
OF Geology must be presented, "a the time was
not scien, for an orderly and complete discussion
Of them. The pressure of the subject upon my o"-
mind. said ne is that Of swollen rushing HOW
while there is but m!-race outlet. ae ieo'
of the las. evenin. closed with SoA.e
of,be theory OF an eynnen, Professor at S>euona'e.
:, cwi,zerland concerning ;he transloitat10' -
rocL. er,ong the Alps and other regions "he'e i0e
..a..o;,od !. mean, of glaciers. de did not sup
an ,,anspor,ation 81 great mineral masses
% he seer, was caused in this way; but
j.. believed that this The true method OF &C
counting for tie phenomenon as II was eHa'Dttso
.,ao,c The Alps and other Alpine regions-and by
Anime regions he meant those in which the tops
&C tho mountains reached the hight OF perpetual
snow, which at the equator was about three miles,
This distance diminishing we 50 froathe equator
in either direction.
There IS one important addition to this theory,
which have not yet noticed: mem the trans
portation of 5oulderstoncs, as they are called By
means OF noatiag ce.-1tis not at all necessary
10 draw upon the imagination TO understand TINS
fact: for it is & matter of observation that ice
islands of vast magnitude arc frequently torn away
from their beds and hoa,cd through Hudson and
Bafia's Bay to more southern regions. have
seen myself ice-isluHds floating through the ocean,
towering from one hundred and fifty to ;wo hun
drcd feet above the surface ef the sea; and as we
know that floating ice never shows above the sur
face moro than eighth of its bulk we may rea.
sonably conclude that islands Ut sixteen hundred
feet in thickness frequently float from The Arctic
regions TO more southern clAles 1t Is easy TO see
then that these Islands easily capable of trans
porting immense loads Of rocks, far more heavy
than the largest ships of war. In one instance
Mr.. Lyell observed a rock which must have weighed
at least fifty thousand tons. 1t is obvious that
when these islands float into warmer regions they
must melt and drop their load; thus the rocks arc
deposited in the bottom OF he Southern which
come from the most Northcrn regions These
masses transported thus, may be seen of the asst
Coast of South America and at the island OF Chi
loe and the process has long been going on. i,
now, and will be in progress forever
AS an example of this, Prof Silliman exhibited
a drawing of rock Of red felaspar granite, some
fifteen feet in length and ten in breadth, resting
on seven marble pillars, in Inclined position,
the pillar at the lowest end being much larger
than the others, iu.tas we may suppose strong
man TO support the heavy end of burden which
it requires six ordinary men at the other end to up
hold. Now how is this position TO be accounted
for-snce the country in that section is all mar
bic and there is no granite to be found there and
here | am happy to say that any OF you in your
next summer excursion may see this most beautiful
object since it is at New Salem, not far from New
Bedford where Gov. JAY once lived: you
easily crawl under it. If may be allowed to sug
gest my mode of accounting for 1t, should
say thai when that section of country was under
the ocean, as 1t may be proved to have been at
some time the granite rock was transported thither
by Al iceberg, dropped to the bottom Of the sea,
and thus deposited upon the sand and mud which
covered the limestone rock, which was aflerward
worn away, and the pillars left standing. Thus
this immense mass was laid down in the place
where it is now found as gently you would lay a
baby in crade-for if it had come tumbling
along like a torrent, it would have crushed every
thing before it. Theirs is also immense rock
found poised upon cilat Land, s End, near Corn
wall in England, SO celebrated for its tin mines-sc
accurately poised that it is very common for travc
lers to visit ii and to rock it upon its sustaining
point with their hands from this circumstance it
is called the rocking rock. By frequent rocking,
the point has become so worn that 1t cannot now
be rocked easily before, and found it difficult
to move it with my shoulder. An English frigatc
IL few years since anchored that place and the
crew. not being geoogists, in a sailor troiic could
think of nothing better forthcir amusement than
to tumble down this rock. The people about there
IL, oh
lect of great and curious Interest," and in their
cenrition the next thing these sailors cond do
was TO get a capstl and hoist itup again. In
New Brunswick, \. j. and all along on the Cats
kill mountains may be found stones composed en-
,irely of the pebbles and sand usually found upon
the sea-bcnch-either cemented By their natural
sediment or by uctua! crystaliAaton. Thus we
prove that the mountains are raised from the
the discoveries Of Nlai.r Mitchell in Austria also
contribute greatly TO this branch of the general
subject. We find rocks of singular composition
near Newport r. lat u place called Purgatory
where there is assure in the rock, and large
pebbles OF u yard in diameter are found hard,
hinty, rounded ut the ends and placed all in one
direction, Just like fleet OF ships at anchor-all
their stcrns in direction, turned thus hy the
current and have no doubt this appearance was
accustomed in the same way by strong current g.
the ocean. 1t is common feat al galluntry for
young men to exhibit,hcr agility by eaping across
this chasm in the presence of those whsse admi-
.ation the seek; and the place thus TO be
called Pursa,oiy-and, so it would beift hey should
fall inte it. In Hercfordshre England, a gres,
abundance OF such rocks may be found, continuing
most beautiful pebbles ana looking much like
plum pudding petried, whence. indeed, they de-
rive their name.
We will now pass TO the rocks which arc found
lying upon the clay slate, called by a distinguished
German Gco!osst, Werner, transition rocks, be-
cause they gre placed midway between the granite
or primary rock and the secondary. They lie tie