he moonlight shining upon it,
so it looks just like a large new moon. It really serves as a moon to
our moon, but its phases follow each other in reverse order. Thus, when
the moon is full, the earth's disc is all dark, and when the moon is in
its first quarter the earth, as seen from there, would be in its third
quarter, and so on through all its phases. Do you follow all that,
M'Allister?"

"Well, mon," replied M'Allister, with a sly grin, "I've just heard you
say it; but"--and here he turned to me--"is it all correct, Professor?"

"Yes, quite correct," I answered, greatly amused at his distrust of
John's statements.

"M'Allister, you're like the Apostle Thomas," commented John, evidently
a little nettled; "so you really doubted my word after all!"

"Heh, mon," he answered, "you're not the Professor, you know; and I
thought maybe you were pulling my leg!"

"Well," laughed John, "perhaps you _will_ get your leg pulled the next
time I condescend to give you a lesson in astronomy!"

After this little spar between my two colleagues we proceeded to the
machine-room, which John and I carefully inspected, to make sure that
all was working properly; and having satisfied ourselves on this point,
we gave M'Allister his instructions for the 'night'; though of course
there was no night now.

Mounting the steps of the conning turret, we then had a look at the
earth, from which we were so rapidly moving away. It appeared about
fifteen degrees in angular diameter, showing that we had travelled some
thirty thousand miles from it.

The full moon, as seen from the earth, appears just about half a degree
in diameter--sometimes a little more, sometimes rather less; so the
earth was apparently about thirty times the diameter the moon usually
appears to us. It was only a thin crescent where lighted by the sun, but
well might M'Allister describe it as "enormous," for it appeared still
larger to him when he saw it some thirty minutes earlier and mistook it
for the new moon.

When we came down again John, very thoughtfully, said to me, "Professor,
you have had a very long, tiring day; and when we reach the moon, we
shall probably stay up several hours to look at it, so you had better
take as long a sleep as possible. There will be no need to break your
rest, for I'm the younger, and will get about by six o'clock, and
relieve M'Allister, who can go on all right up to then, as he has three
hours less work to his credit than we have t