The usual form of reflection seismograph operates satisfactorily over simple structural conditions, but frequently fails to obtain part or all of the desired information when structures are steeply folded, faulted or otherwise complicated. The reasons for this are plainly evident if the paths of the waves in the earth can be visualized. This has been done by the use of a technic originally developed for acoustical measurements.A miniature explosion radiates waves into various models of structure, where reflection and diffraction take place in the same manner as in the earth. The various moving waves are actually photographed in flight. A series of plates is presented, showing wave patterns in various types of structures, ranging from simple to complex. A new type of equipment and technic are briefly described, with which exploration may be carried into the more complex structural regions successfully.