Theories come and theories go-scientific theories. I recall that there was once a theory that Time and Space moved forward constantly in a straight line. There was also a theory that neither Time nor Space existed-it was all in your mind's eye. Then came the theory that Time and Space curved in upon themselves. Tomorrow, some scientist may show us reams and reams of paper and hundreds of square feet of blackboard covered with equations, formulae, signs, symbols, and diagrams to prove that Time and Space curve out away from themselves. Then our theoretic universe will come tumbling about our ears, and we shall have to start all over again from scratch.

Like many fighting men, I am inclined to be credulous concerning matters outside my vocation; or at least I used to be. I believed whatever the scientists said. Long ago, I believed with Flammarion that Mars was habitable and inhabited; then a newer and more reputable school of scientists convinced me that it was neither. Without losing hope, I was yet forced to believe them until I came to Mars to live. They still insist that Mars is neither habitable or inhabited, but I live here. Fact and theory seem to be opposed. Unquestionably, the scientists appear to be correct in theory. Equally incontrovertible is it that I am correct in fact.

In the adventure that I am about to narrate, fact and theory will again cross swords. I hate to do this to my long-suffering scientific friends; but if they would only consult me first rather than dogmatically postulating theories which do not meet with popular acclaim, they would save themselves much embarrassment.

Dejah Thoris, my incomparable princess, and I were sitting upon a carved ersite bench in one of the gardens of our palace in Lesser Helium when an officer in the leather of Tardos Mors, Jeddak of Helium, approached and saluted.