The Madison journal., 1914-08-01

mine the rigdty Of the earth are intensely inter-
esting Science has long needed to know the
physical properties Of this globe. 1t is imposs
BILE to learn this directly as the deepest mines
yet sunk penetrate less than two miles below the
surface, distance proportonately no greater
than the thickness Of the varnish on twofoot
globe The interior Of the earth is believed to
be intensely hot This theory is based on the
fact that molten lava is thrown forth by eruptng
volcanoes. Also in descending a mine. there is a
rise in temperature amounting to so degrees per
mile of descent. If this rate of increase is con-
slant, the temperature at only 100 miles down is
above the melting point of all substances under
conditions as they exist the surface of the
earth However despite the high temperature
the interior of the earth may be held in solid
state by the tremendous pressure to which 1t Is
subjected,
Under the now accepted theory of the celestial
mechanics. scientists assume that a heavenly
body is held in its by the attractive force
exerted by the other heavenly bodies on all sides
of 1t. In this way is determined the earth's
course around the sun and the motion OF the
entire solar system through space. Assuming
that the earth is not a solid mass scientists have
long struggled to discover how 1t resisted the at
tractive forces exerted by other planets and stars
whether as a viscous as a perfectly
elastic body.
They have long known that the earth did re-
sist these forces in some degree. The ocean
tides which sweep our snOreS tWice udHy are
proof of this. It has long been known that the
tides are caused by the attraction of the sun and
the moon. IL the earth offered no resistance to
this attraction. the whole earth would respond
quickly to II and there would be no tides. On
the other hand II the earth were perfectly rigid
body II would resist this attraction completely;
and the tides would reach their maximum height.
The amount that the tides fall short OF their
theoretical maximum height would measure the
degree of rigidity which the earth possesses.
The next step to determine the actual
height Of the tides. This long proved the STUN
bling block II shore lines were perfectly straight
and the floor of the ocean perfectly level, the
height Of the tides could be measured Directly
but crooked shore lines and shelving beaches re-
sist the motion Of the tides and make I: impos-
sibe to determine their height with the accuracy
demanded by science.
/ Sir George Darwin made elaborate experiments
to determine the height of the tides. but was
obliged to give up the problem in despair Pro-
fessor Nicholson solved this difficulty by laying
two lengths Of pipe each ive hundred feet long.
end measuring the rise and fall OF the water In
them. One length of pipe was laid north and
south, and the other length east and west IN
order TO measure the tides in both directions.
The pipes we're buried six feet under ground to
obtain a uniform temperature
At both ends Of the pipes tees were inserted
having glass windows for observatory purposes.
The pipes were half filled with water: and the
changes in the height Of the water were obtained
BY measuring through Q microscope the distance
between a pointer inserted Just under the surface
of the water and the image Of the pointer reflect
ed above the water.