“A fascinating example of patient observation, sound judgment, and acute reasoning. Under Professor Judd’s skillful treatment the volcano is forced not only to tell its own history, but also to solve a number of earth problems seemingly disconnected with it; and the story is told in strong, nervous language, and with an earnestness and subdued enthusiasm that are delightfully stimulating.”—_Boston Gazette._ “Professor Judd first points out the errors in the old definition of a volcano. The volcanic hole is very often not on the summit, but on the side, sometimes at the base of the mountain or hill, and it sends forth steam rather than smoke, and the supposed raging flames are nothing more than the glowing light of a mass of molten material reflected from those vapor-clouds. So our old ignorance vanishes, and in this admirable work the internal structure of volcanic mountains, the nature and products of volcanic action, and the distribution of the materials rejected from volcanic vents, the succession of operations taking place at volcanic centers, are all very ably and clearly discussed.”—_Philadelphia Times._ “A succinct and excellent treatise on a very interesting subject.”—_Philadelphia North American._ • • • • • _For sale by all booksellers; or sent by mail, post paid, on receipt of price._ • • • • • New York: D. APPLETON & CO., 1, 3, & 5 Bond Street. THE CONCEPTS AND THEORIES OF MODERN PHYSICS. =By J. B. STALLO=. • • • • • 12mo, cloth $1.75. • • • • • “Judge Stallo’s work is an inquiry into the validity of those mechanical conceptions of the universe which are now held as fundamental in physical science. He takes up the leading modern doctrines which are based upon this mechanical conception, such as the atomic constitution of matter, the kinetic theory of gases, the conservation of energy, the nebular hypothesis, and other views, to find how much stands upon solid empirical ground, and how much rests upon metaphysical speculation. Since the appearance of Dr. Draper’s ‘Religion and Science,’ no book has been published in the country calculated to make so deep an impression on thoughtful and educated readers as this volume.... The range and minuteness of the author’s learning, the acuteness of his reasoning, and the singular precision and clearness of his style, are qualities which very seldom have been jointly exhibited in a scientific treatise.”—_New York Sun._