An account of the author's investigations in psychical research, together with those of other European savants. Contents: certain unknown natural forces; my first seances in the Allen Kardec group; experiments and other seances with Eusapia Paladino; frauds, tricks, deceptions, impostures, mystifications, impediments; experiments of Count De Gasparin; researches of Professor Thury; experiments of the Dialectical Society of London; experiments of Sir William Crookes; sundry experiments and observations; my general inquiry respecting observations of unexplained phenomena; explanatory hypotheses, theories and doctrines.