Page:Popular Science Monthly Volume 4.djvu/777

 of good habits, self-reliance, and dexterity of hand.

is an address delivered before the Medico-Legal Society of New York, in March, 1873. It discusses the effects of age on the mental faculties, as evidenced in the works of the greatest men of all times. The author states that his method was to study the biographies of such men, and observe the average age at which their best works were produced. The conclusion reached is, that the best work is done between thirty and forty, the worst between seventy and eighty, and that the growth, maturity, and decay, of the mind, are coeval with the corresponding stages of the body. As a corollary, it is held that the moral faculties also decay with the downward curve of life. The fact is pointed out that one or more of the moral faculties may decay, while the rest remain sound. The address concludes with an earnest protest against the prevailing mode of testing moral responsibility in courts of law, and recommends, as an improvement, the appointment by the States of an examining commission, composed of from three to five psychological experts. It is both interesting and instructive.

book is a condensed statement of the principal geological and biological truths and such astronomical facts as relate to the earth. In the introductory chapter, the author thus describes the sphere of his subject: "Physical geography takes up the results achieved in all these departments—geology, biology, and astronomy—and proceeds to higher generalizations.. It shows how the behavior of the earth, as a body in space, and its relations to other bodies, determine the atmospheric currents, and, through them, the movements of the ocean; it points out how the ocean-currents modify and are affected by the tides; it determines the extent to which the character and variation of the climate are dependent on secular changes. The changes of sea and land, as ascertained by the geologists, are used to explain the movements of organized forms, and the biologist finds, in atmospheric, topographical, and climatal influences, the key to the presence or absence, the abundance or scarcity, of particular groups in any locality."

In connection with the composition of the earth's crust, are described the classification, formation, and chemical constitution of rocks; also the production and geological importance of fossils. The configuration of the earth's surface, or the distribution of land and water, with the changes it has undergone; the formation of islands and continents; ocean and atmospheric currents; forms of water in the atmosphere, as snow, rain, mist, etc.; climate and weather, are briefly though clearly set forth. Apparently the only fault of the book is that less space has been devoted to describing the distribution of plants and animals than the importance of the subject demands. As may be inferred from its nature, the book contains no new truths, but its value suffers no impairment therefrom. It has the merit of being free from the influence of particular theories, and, where unsettled questions are discussed, the author conscientiously endeavors to give the reader the drift of scientific opinion.

origin of chemistry is herein traced through the grotesque alchemic vagaries of the middle ages to the natural philosophy of the ancient Greeks and their contemporaries. The quaint admixture of truth and error, constituting their so-called natural philosophy, is first shown. The ideas of primary elements and their transmutations; the metals known to the ancients and the manner in which they were worked; ancient colors and chemical compounds, are all described in a manner calculated to please the general reader. The origin of alchemy is traced to Arabia about the fourth century The mysteries of alchemy are likewise detailed, as well as the theories of combustion and phlogiston, out