Page:Book of record of the time capsule of cupaloy (New York World's fair, 1939).djvu/49

 over, and then decrease as the coil moves farther away.

Second: Take readings along lines at right angles to the measurements suggested in the first method above. These readings should be taken approximately five to ten feet apart, extending fifty to one hundred feet each side of the plane of the energizing coil. The lines of observation should cross the first line every five feet. Observe the position of maximum current in the pickup coil. In an undisturbed field the coil should stand vertically. As the metallic body is approached the position of maximum current in the pickup will stand at an angle from the vertical, and its plane will point roughly to the buried metallic mass. When it passes over the Capsule, the plane of maximum current of the pickup coil will again become vertical. As the coil passes beyond, it will reverse & point in the opposite direction. The strike will undergo a maximum deviation from its normal position as the Capsule is passed.

By a combination of these two methods it should be possible to locate the position of the Time Capsule within a few feet. However, if any other metallic objects lie within the area, they may also give indications. In our day we know of no way to distinguish by geophysical prospecting between different types of metallic substances when they are concealed beneath the ground.