"The _Science of Mechanics_ by Mach, translated by T. J. McCormack, I regard as a most valuable work, not only for acquainting the student with the history of the development of Mechanics, but as serving to present to him most favorably the fundamental ideas of Mechanics and their rational connexion with the highest mathematical developments. It is a most profitable book to read along with the study of a text-book of Mechanics, and I shall take pleasure in recommending its perusal by my students."--_S. W. Robinson_, Professor of Mechanical Engineering, Ohio State University, Columbus, Ohio. "I am delighted with Mach's 'Mechanics.' I will call the attention to it of students and instructors who have the Mechanics or Physics to study or teach."--_J. E. Davies_, University of Wisconsin, Madison, Wis. "There can be but one opinion as to the value of Mach's work in this translation. No instructor in physics should be without a copy of it."--_Henry Crew_, Professor of Physics in the Northwestern University, Evanston, Ill. POPULAR SCIENTIFIC LECTURES. A PORTRAYAL OF THE SPIRIT AND METHODS OF SCIENCE. By DR. ERNST MACH. PROFESSOR OF THE HISTORY AND THEORY OF INDUCTIVE SCIENCE IN THE UNIVERSITY OF VIENNA. Translated by THOMAS J. McCORMACK. _Third Edition, Revised Throughout and Greatly Enlarged._ Cloth, Gilt Top. Exhaustively Indexed. Pages, 415. Cuts, 59. Price, $1.50. TITLES OF THE LECTURES. The Forms of Liquids. The Fibres of Corti. On the Causes of Harmony. On the Velocity of Light. Why Has Man Two Eyes? On Symmetry. On the Fundamental Concepts of Static Electricity. On the Principle of the Conservation of Energy. On the Economical Nature of Physical Inquiry. On the Principle of Comparison in Physics. On the Part Played by Accident in Invention and Discovery. On Sensations of Orientation. On the Relative Educational Value of the Classics and the Mathematico-Physical Sciences. A Contribution to the History of Acoustics. Remarks on the Theory of Spatial Vision. On Transformation and Adaptation in Scientific Thought. PRESS NOTICES. "A most fascinating volume, treating of phenomena in which all are interested, in a delightful style and with wonderful clearness. For lightness of touch and yet solid value of information the chapter 'Why Has Man Two Eyes?' has scarcely a rival in the whole realm of popular scientific writing."--_The Boston Traveller_.