OF RENEWED INTEREST as an intellectual launching pad for historians of technology today is the classic thesis of the late William Fielding Ogburn on the cultural lag in human affairs.' Traditionally, mankind as a whole has reluctantly understood and accommodated itself to dynamic changes in scientific knowledge about nature as well as the technological means available to exploit it. This cultural lag has been rather well documented for the sailing vessel, the telescope, the steam engine, the airplane, and nuclear fission; Ogburn's thesis might well be revisited now, when the pace and the breadth of contemporary technical changes present a wholesale challenge to society in these middle decades of the twentieth century. Until the balloon and the airplane opened up the air space medium, man's physical mobility was only two dimensional. The techniques of war and peace as well as scientific inquiry were thereby constrained. Technologically improved air vehicles, however, exercised a threedimensional influence upon the pursuits of earth-bound mankind. Within the past two decades, moreover, the fourth dimension has been brought sharply into the realm of human comprehension and utility by the release of nuclear energy and the advent of astronautics.