Early geophysical papers of the Society of Exploration Geophysicists earlygeophysical00soci Year: 1947 1326 EUGENE McDERMOTT The question of identifying reflections naturally arises. The most valuable aid in this identification is the use of several recording instru- ments, the movements of which are photographed simultaneously on the same strip of paper. These recorders are arranged as shown in Figure 9. The output of each of these recorders is amplified electrically by the de- sired amount, thus being made to actuate a galvanometer. The motions of the several galvanometers are photographed
Early geophysical papers of the Society of Exploration Geophysicists earlygeophysical00soci Year: 1947 1326 EUGENE McDERMOTT The question of identifying reflections naturally arises. The most valuable aid in this identification is the use of several recording instru- ments, the movements of which are photographed simultaneously on the same strip of paper. These recorders are arranged as shown in Figure 9. The output of each of these recorders is amplified electrically by the de- sired amount, thus being made to actuate a galvanometer. The motions of the several galvanometers are photographed on the same strip of paper. This strip also has timing lines photographed on it so that the time of arrival of each reflection may be determined. Obviously, in Figure 9 the lengths of the four reflection paths from the shot point to the four recorders are not very different. If the recorders are fairly close to the shot point, the time differences between these paths may not be more than a few thousandths of a second and in general are not more than SHOT F?£:cOJ?DE£?S Fig. 9.—Multiple recorders. 44
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