Boiling liquid magma or super hard matter? Inconceivably high temperatures or cold neighboring on absolute zero? What are the depths of the Earth like? What mysteries does its mantle conceal? Science cannot as yet give the exact answers to these questions, though myriads of different hypotheses have been put forth.This is a fascinating book about the romance of prospecting, about the pertinacious investigations of geologists studying the inside of our planet. The author, Professor Anatoly Malakhov, D.Sc. (Geology and Mineralogy) was well known to the Soviet reading public for his previous popular-science books A Hundred Professions of a Geologist and Stories about Stones.