This popular book, designed for young readers who are acquainted with the rudiments of physics and chemistry, is a translation of a Soviet textbook by Academician V. Obruchev. "The person unversed in geology is like a blind man. He cannot distinguish between various rocks. The different colors of rock tell him nothing. He cannot understand how gullies were formed. He sees layers of rock in some gully and wonders why they are strangely twisted in one place, while elsewhere they stand upright. This person may admire a picturesque cliff, an austere canyon or waterfall, but these sights evoke but superficial impressions. He can only appreciate nature's outward forms, but not the substance of the phenomena, he will see but not comprehend. Geology teaches us to understand nature and learn how it developed."