AUTHOR’S PREFACE. My former pupil. Mr. Frederick Prime Jr., a very enthusi astic student in this branch of geology, has received my full approval and permission to translate my book on Ore Deposits. I have suggested many alterations, and additions, which he will set forth in this translation; so that, as a whole, it may be con sidered as a new edition (the third one) of my work. From the attention I have given to it, as the translation progressed, I feel justified in approving it as a whole. B. von COTTA. Freiberg, January, 1869.