"Heh, Professor," he interjected, "I know I couldn't see the moon if it was straight ahead of our course, but then what about that enormous new moon that's behind us? I saw that right enough."
"That enormous new moon, M'Allister, is only our own little world which we left a few hours ago," I replied.
He stared at me as though bewildered, and after pondering a while, exclaimed, "Losh, mon, you surely don't mean to say that our own little world changes about in the same way as the moon does--sometimes new and sometimes full?"
Here John interposed. "Yes, M'Allister, you can take it from me that it is just what our world does do. I think you are aware that, like the moon, our world simply reflects the light it receives from the sun, and does not shine by its own light. So one side is light and the other side is dark, according to its position in regard to the sun. From our present position we are only able to see a small portion of the lighted side, the remainder being dark except for the 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.