"The book summarizes the results of the men who have accomplished the great things in their pursuit of seismological knowledge. It is abundantly illustrated and it fills a place unique in the literature of modern science"—Chicago Tribune.

15.—The Nature of Man. Studies in Optimistic Philosophy. By Élie Metchnikoff, Professor at the Pasteur Institute. Translation and introduction by P. Chambers Mitchell, M.A., D.Sc. Oxon. Illustrated. 8°. Net, $1.50.

"A book to be set side by side with Huxley's Essays, whose spirit it carries a step further on the long road towards its goal"—Mail and Express.

16.—The Hygiene of Nerves and Mind in Health and Disease. By August Forel, M.D., formerly Professor of Psychiatry in the University of Zurich. Authorized Translation. 8°. Net, $2.00. (By mail, $2.20.)

A comprehensive and concise summary of the results of science in its chosen field. Its authorship is a guarantee that the statements made are authoritative as far as the statement of an individual can be so regarded.

17.—The Prolongation of Life. Optimistic Essays. By Élie Metchnikoff, Sub-Director of the Pasteur Institute. Author of "The Nature of Man." etc. 8°. Illustrated. Net, $2.50. (By mail, $2.70.) Popular Edition. With an introduction by Prof. Charles S. Minot. Net, $1.75.

In his new work Professor Metchnikoff expounds at greater length, in the light of additional knowledge gained in the last few years, his main thesis that human life is not only unnaturally short but unnaturally burdened with physical and mental disabilities. He analyzes the causes of these disharmonies and explains his reasons for hoping that they may be counteracted by a rational hygiene.

18.—The Solar System. A Study of Recent Observations. By Prof. Charles Lane Poor, Professor of Astronomy in Columbia University. 8°. Illustrated. Net, $2.00.

The subject is presented in untechnical language and without the use of mathematics. Professor Poor shows by what steps the precise knowledge of to day has been reached and explains the marvellous results of modern methods and modern observations.

19.—Climate—Considered Especially in Relation to Man. By Robert DeCourcy Ward, Assistant Professor of Climatology in Harvard University. 8°. Illustrated. Net, $2.00.