Evening star. [volume] (Washington, D.C.) 1854-1972, 1906-10-20
NEW REVELATION OF RADIUM.
Determining the Thickness Of the
Crust of the Earth.

From the London Telegraph. ia.
Still another wonder of radium! The lat
est revelation Of that remarkable element
is to tell us something of the thickness Of
the earth's crust and the heat Of our globes
internal fires. How this comes about is
part Of the fairy tales Of science.
Emergencies of opinion between the geol-
ogists and the physicists regarding the
thickness to be assigned to the solid crust
Of the earth are of long standing. Thanks
to the late M. Curie. and Nine. Curie. the dis
coverers of radium. and to the researches
of Prof J. ]. Thomson and Prof Ruth
erford, the physicists are now armed with
a weapon Of research of which former
savants had no idea. 1t will be remembered
that about three years ago r. J. Strut,
F. R: s., son Of Lord Rayleigh. detected ra-
dunn in the deposit left by the waters of
the hot springs Of Bath. He has also writ
ten a work on the new element entitled
THE Becquerel Rays and the Properties OF
Radium." Following up his investigations.
Mr. Strut has for a considerable time been
engaged in an estimation Of the average
amount Of radium contained in the repre-
sentative rocks OF the eearth's exterior.
He has gathered specimens Of granite
from Cornwall and Rhodesia; basalt from
the Giants Causeway. Greenland, and the
Victoria Falls; serpentine from the Lizard:
syenite rocks from Norway. and leucite
from Monte Somma. Vesuvius: compelling
each and all Of these to yield their secret.
First Of ALL the several rock fragments
were decomposed by chemical agency, and
then the radium present was determined
quantitatively by its "emanation." This
emanation. in consequence Of its slow decay
Of activity. may be stored mixed with air.
in an ordinary gashOlder. and it's photo
graphic and electrical action can be ex-
amined for several days. or even weeks.
afterward, quite apart from the radium
from which 1t was obtained. Mr.. Strut
stored rock solutions until the required
emanations had accumulated They were
then each extracted by boiling. and intro
duced into special type of that refined in
strument for accurate measurements. the
electroscope. thereby affordng an indica-
ton Of the amount OF radium present. The
measure was made absolute by going
through the same process with a uranium
mineral of known radium content.
The presence Of radium. whether there
he relatively much or little of 1t, can easily
be denoted in all tgneous rocks In gen.
eral the GRANTEES hold most and the basaitic
rocks least. Moreover, from its uniform
distribution the total quantity in each mile
visionally calculated. Mr.. Strut Is of the
opinion that not more than one-thirtieth
of the earth's volume can consist Of ma
terials similar to those encountered on it's
surface, and, from various mathematical
and physical considerations he allows
depth of forty-five miles for the rock-crust
of the globe. suggesting further that the
maximum temperature of the bottom Of
hood of 1.50O degrees Centigrade Cor 2,7O0
degrees Fahrenheit). fifteen times the tenn
perature of boiling water. This is the
melting point of iron. that of silver be-
ing LOCO degrees Centigrade and gold ,250
degrees Centigrade. But 1t is considerably
below the melting point Of platinum, which,
according to recent determination by DR..
]. A. Harker. is 1. 10 degrees Centigrade.
This result with regard to the thickness
Of the earth's crust may be compared with
the conclusion arrived at by Prof. John
Milne. F. r. s., the distinguished seismolo-
gist, lately put forward in his Bakerian
lecture. Prof Mines study of the speeds
of earthquake tremors. propagated through
the globe, led him to think that at dorth
of thirty miles below the earth's surface
q maximum depth is reached, at which
there are materials having physical prop
critics similar to those on the surface. There
would seem to be little in common between
earthquake tremors and radium, but they
tell tale In very fair agreement as to the
extent downward of the earth's solid crust.
A still more curious outcome of this tnves-
tigation remains to be noticed-one touch
ing the condition Of the moon. Mr.. Strut
thinks that the view of some astronomers,
in particular of Mr.. w. H. Pickering, that
the moon is not dead" but still exhibits
volcanic action, is on the whole reason
able assumption. He also thinks, what Is
certainly surprising, that It's internal heat
must be far greater than that Of the earth