SCIENTIFIC LECTURES AND ESSAYS. 



Popular Lectures on Scientific Subjects. By H. 



HELMHOLTZ, Professor of Physics in the University of Berlin. First 

 Series. Translated by E. ATKINSON, Ph. D., F. C. S. With an Intro- 

 duction by Professor TYNDALL. With 51 Illustrations. 12mo. 

 Cloth, $2.00. 



CONTENTS. On the Relation of Natural Science to Science in General. 

 On Goethe's Scientific Researches. On the Physiological Causes of Harmoi.y in 

 Music. Ice and Glaciers. Interaction of the Natural Forces. The Recent Prog- 

 ress of the Theory of Vision. The Conservation of Force. Aim and Progress 

 of Physical Science. 



Popular Lectures on Scientific Subjects. By H. 



HELMHOLTZ. Second Series. 12mo. Cloth, $1.50. 

 CONTENTS. Gustav Magnus. In Memoriam. The Origin and Significance 

 of Geometrical Axioms. Relation of Optics to Painting. Origin of the "Planetary 

 System. On Thought in Medicine. Academic Freedom in German Universities. 



" Professor Helmholtz's second series of * Popular Lectures on Scientific Sub- 

 jects 1 forms a volume of singular interest and value. He who anticipates a dry 

 record of facts or a sequence of immature generalization will find himself happily 

 mistaken. In style and method these discourses are models of excellence, and, 

 since they come from a man whose learning and authority are beyond dispute, 

 they may be accepted as presenting: the conclusions of the best thought of the 

 times in scientific fields." Boston Traveler. 



Science and Culture, and other Essays. By Pro- 

 fessor T. H. HUXLEY, F. R. S. 12mo. Cloth, $1.50. 



"Of the essays that have been collected by Professor Huxley in this volume, 

 the first lour deal with some aspect of education. Most of the remainder are ex- 

 positions of the results of biological research, and, at the same time, illustrations 

 of the history of scientific ideas. Some of these are among the most interesting 

 of Professor Huxley's contributions to the literature of science." London Acad- 

 emy. 



"It is refreshing to be brought into converse with one of the most vigorous 

 and acute thinkers of our time, who has the power of putting his thoughts into 

 language so clear and forcible." London Spectator. 



Scientific Culture, and other Essays. By JOSIAH 



PARSONS COOKE, Professor of Chemistry and Mineralogy in Harvard 

 College. 12mo. Cloth, $1.00. 



These essays are an outcome of a somewhat large experience in teaching 

 physical science to college students. Cambridge, Massachusetts, early set the 

 example of makine the student's own observations in the laboratory or cabinet 

 the basis of all teaching, either in experimental or natural history science ; and 

 ihis example has been generally followed. " But in most centers of education," 

 writes Professor Cooke, " the old traditions so far survive that the great end of 

 scientific culture is lost in attempting to conform even laboratory instruction to 

 the old academic methods of recitations and examinations. To point out this 

 error, and to claim for science -teaching its appropriate methods, was one object 

 of writing these essays." 



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