| 摘要 |
A device for generating acoustic waves in the earth by striking a mass, housed in a guiding tube, against a target member secured to the lower end of this tube and coupled to the earth in operating conditions, including means, such as an electromagnet, for holding said mass at the upper end of said tube and releasing it at will, and means to turn the tube upside down after each operation so as to reset the mass in position for a new operation. |
