A purpose of science is to organize diversified factual knowledge into a coherent body of information, and to present this from the simplest possible viewpoint. This is a formidable task where our knowledge is incomplete, as it is with explosions. Here one runs the risk of oversimplification, naivete, and incom­ pleteness. Nevertheless a purpose of this work is to present as simply as possible a general description of the basic nature of explosions. This treatise should be of interest to all who are working with explosives such as used in construction or in demolition work, in mining operations, or in military applications. It should also be of interest to those concemed with disasters such as explosions or earthquakes, to those involved in civil defense precautions, and to those concemed with defense against terrorists. That is, this material should be of interest to all who wish to utilize, or to avoid, the effects of explosions as weil as to those whose interest is primarily scientific in nature.