| 摘要 |
<p>The appts. includes a cable provided on its bottom end with a wt., lowered into a hole drilled in the earth. The cable is first provided with a vertical row of boxes, which each contain explosive charges, a support for a detonator with electric contacts. The cable passes through each box; and a bundle of electric wires also passes vertically through each box so the detonators in all the boxes can be fed with an electric current causing an explosion. The detonator consists of a tube provided with contacts on its bottom end, these contacts mating with a pair of contacts fixed in the box and connected to two of the bundle of electric wires. Used for example, a hole 50-175 metres deep is drilled in the earth. The boxes are exploded while seismographs on the surface of the earth analyse the shock waves to determine the type of earth at various depths.</p> |
