The book of the most prominent English geophysicist K.E. Bullen, one of the creators of modern ideas about the structure of the Earth, has become a reference book for all specialists studying the Earth. The author sets out the foundations of the theory of elasticity as applied to seismology, considers the theory of elastic waves propagating in the Earth, and analyzes the results of their observation for the study of deep subsoil and surface layers. The new edition includes chapters on the Earth's own vibrations, the effects of underground nuclear explosions, and extraterrestrial seismology. The book is of great interest to geophysicists and geologists, both students and specialists. It will also be useful for astronomers studying the planets of the solar system, as well as for military specialists.