Interplanetary commerce, if and when it begins, will be fraught with all of the dangers that accompany pioneering expeditions. There will be the terrible climatic conditions on other worlds to be faced, strange beasts and plants; and perhaps desperate and greedy men. That was the case when every new land was opened on Earth and it may be expected to be true when we conquer the solar planets. Mr. Jones understands these things well. His vivid imagination, his sense of a good story and his knowledge of what may be expected upon other worlds combine to make this a novel and exciting yarn. And, as is always desired, it comes to a smashing finish with a surprising ending. His scientific weapons are quite novel, but so realistically does he portray them, that they strike one as being quite possible and likely to be used at some future time.