Remarks on multiple reflections

One cannot help being impressed by the wonderful arrays of seismograms depicted in Mr. Ellsworth's paper and in the prepared discussions. The regularity of the time intervals of successive impulses and the alternating sequence of the change of phase are readily adapted to a mechanism of multiple reflections. If the latter is accepted, the following questions seem to merit some consideration: (a) the energy concentration, (b) the positions of the reflecting surfaces, (c) the sharpness of the source-impulse, and (d) the velocity contrast of the adjacent media.