erence in the velocities of Mercury and the earth
in their revolutions around the sun, one synodic revolution of
Mercury, _i.e._, from one inferior conjunction to the next, requires
nearly one hundred and sixteen days. In eighty-eight days Mercury has
completed her sidereal revolution, but during that time the earth has
moved ahead a distance requiring twenty-eight days more before she can
be overtaken.

After the first week in March of this year therefore Mercury will
again be approaching inferior conjunction, and again will pass at her
closest point to the earth.

We may expect at this time another bombardment of a severity that may
cause tremendous destruction, or destroy entirely life on this planet!

CHAPTER II.

THE UNKNOWN ENEMY.

When, in February, 1941, Professor James Newland issued this remarkable
statement, my paper sent me at once to interview him. He was at this time
at the head of the Harvard observatory staff. He lived with his son and
daughter in Cambridge. His wife was dead. I had been acquainted with the
professor and his family for some time. I first met his son, Alan, during
our university days at Harvard. We liked each other at once, and became
firm friends--possibly because we were such opposite physical types, as
sometimes happens.

Alan was tall, lean and muscular--an inch or so over six feet--with the
perfect build of an athlete. I am dark; Alan was blond, with short, curly
hair, and blue eyes. His features were strong and regular. He was, in
fact, one of the handsomest men I have ever seen. And yet he acted as
though he didn't know it--or if he did, as though he considered it a
handicap. I think what saved him was his ingenious, ready smile, and his
retiring, unassuming--almost diffident--manner.

At the time of the events I am describing Alan was twenty-two--about two
years younger than I. It was his first year out of college. He had taken a
scientific course and intended to join his father's staff.

Beth and Alan were twins. I was tremendously interested in Beth even then.
She seemed one of the most worth-while girls I had ever met. She was a
little wisp of femininity, slender and delicate, hardly more than five
feet one or two. She had beautiful golden hair and an animated, pretty
face, with a pert little snub nose. She was a graduate of Vassar, and
planned to take up chemistry as a profession, for she had the same
scientific bent