, 1860-03-16

The lecture on Geology By Prof. James Hall
Of Albany, y. T., before the chica do Academy
Of Sciences, ut Dearborn Institute last evening,
was delivered to M intelligent'aud appreciative
audience. The 81 eaker is one of tic most dis
tinguished of American sarans in his branch
of science, and the author of 4 celebrated trea-
tise on Paleonto1ogy. The lecture was the re-
rerse Of formal, but was all the more valuable
and attractive to the listeners. Our abstrac: Of
report does it feeble justice.
Tbs lecturer commenced By remarkiug that
the development Of Geology has had much to
do with the progress of civilization. By fixing
the sequenee Of rocks, and enabling us to deter
mine with precision Tic presence or absence OF
coal or other useful Minerals.
Geology has claims Of importance as disci-
plinary study. It has an Important influence
upon intellectual growth. Man is fixed to the
earth Ike t1ee, though the planet is only bis
transient abiding place. He draws his susie
nance in all respects from the earth.
Sand, clay and lime constitute the bulk Of The
earth; these deposits ara widely distributed;
they were formed in M ocean which once cx-
tonded over the whole continent; We know this
from the aact that these rocks contain organic
forms and consist Of material similar these nor
carried down into the sea by storms.
These materials must baye hsen accumulated
more abuudantly in some places than otltra in
the ancient ocean. Hence the strata will be
found thicker at some points than others.
Sometimes beds Of enormous thickness thin out
as we trace t1eu, orer long distances. The
points Of ereatest accumulation mark the
action Of the strongest currents. The Eastern
part Of the United States is mole diversified
by hills and mountains the central Is marked
BY plains. Tie kigiu of the Appalachian chain
is due rather to l4e heaplug UP of vast deposits
the crus. Of the earth. The highest mountains
are always i'll thelocalities where the formations
are thckest.
Thus the Hudson River group is GGc0 OF
5000 feet thick in New York, while in the West
it is only 50 or 100 feet thick. The stratiiea
rocks cover tho principal areas upon the earth's
surface. The Potsdnm sandstone IS the earliest
OF these rocks in which We find any fossils Its
origin was in the West and Southwest. Adore
this sandstone is tho Trenton limestone, which
contains new fossils, especially corals, unu WIS
formed in more quiet waters. Next succeeds
the Hudson Riser group already noticed,
thickest in the disturbed districts Of the East
Niagara group, mainly composed Of limestone,
extensively seen in New York, forming tue
ptecinice over which the waier7 OF tie upper
Lakes are precipisated. Thence it. extends
Westward, and is found developed on the East
shore Of Lake Michigan and West in Iowa and
Aiunesota. 1t is very fossilferou,, and is espec-
ially rich in cora1s.
1hc formations Of The Upper nl1eeserg
Mountains having thickness Ut 3.Ctt sset in
the Appalachian chain and thinning II 1i'y feet
in the Mississippi Valley. The materials in the
east are coarte and west are very fine. The
eastern masses make the pasl, Of the great Gee
anic currents, while the eentley currents have
distributed the impafpab!e mud wsst*urd. Tue
coal formation is next above. East it IS II. 0eo
feet thick; West it is not moro than 200 feet.
During this period there were :rcat disturb
ances. The granite of the White mountains is
of this age. Rocks arc often 1netamorpaosed,
so that limestone becomes marble, soft shells
are hardened into STATE, aud sandstone into
quartz.
ihc Professor then explained a:1d illustrated
by diagrams On the board the courses OF these
complicated unduEasions which occur in the
coal strula of the Appalachian chnin. 1t is by
the accumulation Of deposits upen constantly
| snnken ocean aoor thut lhe strata have been
| wrinkled and unaulated there.
The canscs Of mountain chains, then. is the
| accumulation Of Glc4ter mass es Of matttr aloaE
| their line. llettodox Us this may seem, t!as
| SPEAKER was nurc anu 1roro convinced Of ii.
t;u b. The Rocky Mountains hare the SAINT
origin, their g1saier Elevation being due to th'
fact that there the chalk formation is added It
The other deposits.
The vicws of;1h lecturer we're novel, tu
| werc made cleanby the manner mud illustration
Of the speaker, and were listened to With eyi
| dent interest BY; the members Of the Academy