Page:Popular Science Monthly Volume 47.djvu/721

Rh fixed sun, by their orbital motions around and constant subjection thereto act as enormous induction machines which generate electricity from the ocean of attenuated aqueous vapor, each planet being surrounded by an enormous electrosphere carried with the planet in its axial and orbital movements, the successive atmospheric envelopes gradually diminishing in rotational velocity until merged into the outer ocean of space. As the planets advance in their orbits they plunge into new and fresh fields, and as the whole solar system gradually moves onward through space these fields are never reoccupied. These electrospheres by their rotation generate enormous quantities of electricity at an extremely high potential—so high that we can scarcely even conceive it—and this electricity flows in a constant current to the sun, where it disappears as electricity to reappear in the form of solar light and heat." A chapter is given pointing out the difficulties in the way of accepting present theories. The book is readable and interesting, contains numerous extracts from astronomical authorities, and some well-executed cuts.

second of the little books in the Library of Useful Stories deals with the fascinating science of man, and with that division of it concerning which Dr. Johnson said but little more than a century ago, "We can know no more than what the old writers have told us." A great deal that seemed unknowable in Johnson's time, however, is now known, and Mr. Clodd here gives the general reader a comprehensive view of what we are told by the old river beds, lake bottoms, caverns, sepulchres, and refuse heaps concerning man's doings before there were any writers. Mr. Clodd is well known as the author of The Story of Creation, A Primer of Evolution, and The Childhood of Religions, and is thoroughly acquainted with the subject which he here epitomizes. After discussing the place of man in the earth's life history and the earth's time-history, he describes the implements and other remains of primitive man that have been found, and tells what may reasonably be inferred from them concerning human life at the time they were laid down. He divides this ancient period into the customary ages, but records his conviction that no hard-and-fast line can be drawn between the two stone ages. "The revolution wrought by metals," he says, "is the greatest that the world has yet seen or that it will ever see." Mr. Clodd has fully attained the ideal of the series to which he contributes this little volume. He has succeeded in telling his story in an eminently readable style, explaining all uncommon words that he was obliged to use and avoiding hosts that he might have used. He takes frequent occasion to call attention to the workings of evolution in human affairs, thus showing his emancipation from the sentiment that man is not really a part of Nature, which still hampers some men of science. There are an abundance of instructive illustrations, and for frontispiece the author has chosen the clever picture by Gabriel Max showing the probable appearance of-the "ancestors of man."

chemist of the United States Department of Agriculture has undertaken the task of preparing a comprehensive manual for the estimation of soils, fertilizers, and agricultural products, and the first volume of the work is now before us. After some account of the origin of soils the author describes a variety of methods of taking samples for analysis and the preliminary treatment of the samples. Proceeding to the analysis, he takes up first the determination of physical properties, including behavior to heat, cohesion, adhesion, absorption of salts, and porosity. Another division of the work relates to the flocculation of soil particles and the separation of soil particles by a liquid, together with some miscellaneous determinations, and a chapter is given to estimations of gases. Coming to the chemical examination, methods are given for the determination of potash, lime, magnesia^ manganese, iron, phosphoric and sulphuric acids, chlorine, silica, kaolin, and nitrogen. Some forty pages are devoted to determinations of