The essays contained in this book were written to collect and digest the facts relating to a number of incidents which have not, at present, been satisfactorily explained, quoting extensively from original sources. Contents: Devil's hoof-marks; Vault at Barbados; Ships seen on the ice; Berbalangs of Cagayan Sulu; Orffyreus' wheel; Crosse's Acari; The Auroras, and other doubtful islands; Mersenne's numbers; Wizard of Mauritius; Planet Vulcan; Nostradamus.