"As we regain our weight we shall feel the need of sleep again," he said. "But on Mars we may need but one-third as much as we had on Earth, unless we exert ourselves proportionately more."

Then I told him about the circular spot which had seemed to slip off the upper edge of Mars, and asked his explanation of it.

"That must have been Phobos, one of the moons of Mars," he said.

"One of his moons!" I exclaimed; "I didn't know he had any."

"You are an American, and say that!" he answered in surprise. "It is one of the astronomical glories of your people that they discovered the two moons of Mars, during the favourable opposition of 1877."

"This is the first case I remember where we have left it to a foreigner to tell us how great we have been!" I laughed.

"These two moons of Mars also furnish a most interesting example of how fiction may forestall and pre-figure actual scientific discovery. Dr. Swift made Gulliver, in his wonderful travels, discover two moons of Mars, revolving at a speed which he must have thought ridiculously fast. Many years afterward the American telescopes really found two moons, but actually revolving more rapidly than Dr. Swift had dared to boast! If your white circle was really Phobos, you have seen the freak among satellites. She is the smallest, swiftest moon ever discovered, and travels so much more swiftly than the revolution of her primary that she appears to go opposite to everything else in the Martian sky, rising where the Sun sets and crossing the heavens from west to east!"

"What I saw did travel in the same direction as the rotation of the planet, and much more rapidly," I exclaimed.

"Then it was Phobos without a doubt, and she is due to appear again in the west in three hours and fifty minutes after she sets in the east. We must watch closely, for I wish to land upon her and make a flying trip all around Mars with her. Do you realize what a glorious view we shall have of the great planet, sailing around him on this satellite in a period of a little over seven and a half hours, and at a distance of only about four thousand miles? There will be no night, for if one side of the little moon is heavier than the other, the heavier side will always be turned toward Mars. Therefore, when the Sun does not shine on Phobos, Mars will do so, and keep her continually illuminated, except for the brief period of the regular eclipse during each revolution. And one-fourth of the entire heavens, as seen from Phobos, will be filled with the glowing orb of Mars! The great planet will exhibit to us at a near range all the configurations of his surface, his oceans and his clouds. We will survey and photograph him to our hearts' content."

The doctor was justly enthusiastic on this subject, and I felt that such a landing would, in some measure, compensate for my disappointment in not being able to visit the Moon.