deepen these shafts for several miles would
be much less difficult than most people imagine.

Increasing heat, if it is found that heat does increase, would not be
difficult to overcome had the engineers sufficient money. Ventilation
and transportation to and from the surface, while too costly for the
business enterprise of winning metals from very deep mines, probably
would present no serious difficulty were facts the chief object
instead of profit. The only question to be decided before intending
benefactors of science are urged to consider some such project is
whether or not the facts likely to be won promise enough value to
mankind.

An excellent case can be made out for answering yes. Dr. Shapley
mentioned four chief lines of investigation suitable for such
deep-mine laboratories: studies of gravity and of the variable length
of the day, researches on the various kinds of earthquake waves,
experiments on ether drift and tests of the biological effects of
cosmic rays and of the rays from radium.

Astronomical theories indicate that the day ought to be growing
slightly longer as the earth's rotation decreases a trifle from
century to century because of friction from the tides. The actual
length of the days seems, however, sometimes to be decreasing a tiny
fraction of a second from year to year, as theory says that it should;
sometimes to be increasing in a way for which no present theory
provides. Observations underneath the earth, with a portion of the
planet's crust and gravity overhead, might yield important clues to
the cause of this mysterious wrong time kept by the terrestrial
clock.

The Gray Plague

_By L. A. Eshbach_

[Sidenote: Maimed and captive, in the depths of an interplanetary
meteor-craft, lay the only possible savior of plague-ridden Earth.]

[Illustration: _They were almost upon him when he leaped into
action._]

CHAPTER I

Five months before the beginning of that period of madness, that time
of chaos and death that became known as the Gray Plague, the first of
the strange meteors fell to Earth. It landed a few miles west of El
Paso, Texas, on the morning of March 11th.

In a few hours a great throng of people gathered around the dully
smoldering mass of fire-pitted rock, the upper half of which protruded
from the Earth where it had buried itself, like a huge, roughly
outlined hemisphere. And then, when the crowd had assumed its
greatest proportions, the meteor, with a mighty,