It is easy to thrill to the seeming marvels of our own times, but only the short-sighted thinker believes in the perfection of present scientific progress.  The 300-mile-an-hour airplane which Fraser conceived in this book for the speed of the Sky-Bird II was little more than so many words when he wrote it. . . . today we have 400-mile-an-hour fighting planes.  Today we have in this country an intricate highway system, but perhaps within your own lifetime our highways, and the automobiles which skim over them, will be laughed at as obsolete and useless.