bodies waste not, neither do they become aged nor infirm, and they never die."
Here I interrupted him.
"Do they increase?" I demanded.
"Yes, certainly they do," he responded.
"There is a natural increase," I said, "and no deaths. Mars must surely become over-populated. (I had the over-population question in view ever since I heard of their immortality.) Why, it would only be a question of time for the population to increase so as not to leave standing room for them on the dry land!"
"If you will permit me, I will explain further," he added. "Your inference," he went on, "would undoubtedly be correct, were it not surrounded by other considerations that modify the condition of affairs. There is another luminous planet, compared to which Mars in size is a mere speck, and yet hardly less beautiful than the latter, which comes from the unfathomable depths of space at long intervals of time, calculated to be somewhere about one hundred thousand years, curves round Mars at almost touching distance, then wanders back again in the direction from whence it came, and is lost to view for the period mentioned. Now," he continued, "it is during the time that
