Evening star., 1942-03-13
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Laboratory, Field
And Study
BIZ Thomas r. Henru.

By Thomas r. Henry.
The Adirondacks are approximately
| 1,100 900 900 years old.
First determined at Vienna in 1899
from uranium-lead content of specimens
of urananite in 1899, the age Of these
mountains has just been checked with an
| entirely different type of mineral at the
| United States National Museum here by
DR.. j. P. Marble of the National Re-
search Councils Committee on the Age
| of the Earth.
The two determinations are essentially
identical, within the limits of expert
mental error. Both are very close to
determinations of the age of the So
called Canadian Shield" which includes
most Of Canada north of the st. Law
renee and between the mountains Of
Labrador and the Mckenzie River.
DR.. Marbles study was OF mineral
known as atlantic which contains the
radioactive element thorium. Like
uranium, it degenerates into lead
through radio-activity but at a consid
erably different rate.
The calculated age represents the
time that has elapsed since the rock ma
terials which constitute the mountain
masses were brought together In their
present position. The determination
shows that the mountains existed in
about their present form long before
anything remotely like life, as it is
known today, existed on the earth.
DR.. Marble says geologists long have
known that the Adirondacks were very
old. 1t has been assumed that they were
a southern extension of the Canadian
rocks. There has been, however, no
definite proof. The present evidence OF
Identical ages goes far to establish this
fact.
At present the Adirondacks and the
Canadian Shield are separated by the
st. Lawrence River, which runs through
a channel of much younger rock. Around
these mountains through the ages the
landscape has undergone great changes.
They constitute an island Of very hard
rock, of a peculiar type. surrounded by
relatively soft rock which has been built
up and worn down by wind. flood and
weather many times. The hard mass
itself has been highly resistant-literally
rock of ages" 1t has worn down very
slowly.
The central mass Of the Adirondacks.
DR.. Marble points out. is composed Of
a peculiar type of mineral known as
anothosite. 1t consists OF from 80 to
95 per cent felspar, whereas only about
a third of granite is of this substance.
The high peak region is made up almost
entirely of anothosite. the biggest mass
of 1t on earth. Other large masses of
1t. however, are found in the Canadian
Shield. 1t is an igneous material, at
some time pushed upward from the
depths Of the earth.
At present the mountains have very
thin soil. although parts of them are
rather thickly forested. During the
last glaciations, about $4,000 years
ago. the soil was all scraped of by the
moving ice. DR.. Marble explains, while
deposits were left in the valleys. Trees
began to grow on these shortly after
the retreat of the glaciers. Slowly
seedlings gained foothold in crevasses
of the bare rocks filled with wind
blown dust. Through thousands OF au-
tumns their leaves fell and rotted on the
mountain sides. This formed soil upon
which new seedlings grew. Their leaves.
trunks and branches formed new soil
upon which more trees grew. Thus grad
ually the thin soil covering was created
to Its present thickness.
A few years ago specimens OF the
urananite mineral were collected by DR..
B. NJ Shaub of Smith College. He sent
them to the Vienna laboratory. a world
center for micro-analytical methods. The
specimens of atlantic studied by DR.. Mar
BILE came from site about IS miles away.
The fact that both calcula tions check
so perfectly, although different minerals
and different decay rates are involved,
is regarded as convincing proof that
both are highly accurate. The ana
lytical work necessary is very slow and
subject to experimental errors. Had the
same materials been used there would
have been q possibility that both ana
lyzers had made the same errors.
The crocodile, one Of earth's Oldest ex-
tAnt animals. Is growing smaller and
u uGCic 1CoS 1CiONlOuo Will dSC.
They were giants. probably half again
as big as today, about 100 1000 900 years
ago. Before that they may have been
even bigger.
One of the largest yet known has
Just been described from the collections
of the Smithsonian Institution by DR..
Charles C. Nook of Brooklyn College.
The fossil was collected in Venezuela
by a Catholic brother few years ago.
The crocodile first appears in the
world, according to DR.. Charles w. Gil
more of the Smithsonian staff, about
170,000000 years ago with the second
horizon Of the dinosaurs If the COM
plete record was found it probably would
be entirely contemporaneous with its
fellow-reptiles, some of whom obtained
enormous size and became the masters
Of the earth.
The crocodile made no such mistake.
It was more conservative than the dino
saur and probably more ruthless and
cruel than most of the monsters. 1t
was only very distantly related to them
through common ancestry in the giant
amphibians, the first forms of vertebrate
life to appear on the land.
Dinosaurs changed with prosperity,
became highly adapted to their environ
ment, and were unable to survive when
this changed. The crocodile prospered
4