The present work by the German researcher and geographer Wilhelm Volz is his report on an expedition conducted from 1904 to 1906 on behalf of the Humboldt Foundation of the Royal Prussian Academy of Sciences in Berlin. One of the main objectives of this journey was to investigate the geological structure and volcanoes of Sumatra. Volz impressively and thoroughly describes his journey, which took place with a military escort from the Dutch colonial government. He supports his descriptions with a wealth of illustrations. This book is a reprint of the long out-of-print original edition from 1912.