Page:Popular Science Monthly Volume 4.djvu/776

 a single township, amounts to something almost incredible when an entire State or country is included in the calculation. According to the reports of Dr. Fitch, $12,000,000 worth of wheat has been destroyed in the State of New York, in a single year, by the wheat-midge and Hessian-fly. An interesting account is next given of the reproduction, growth, and metamorphosis, of insects, with some remarks on their psychology, their relations to each other, and their relations to other animals. The last twelve pages are devoted to the insects of the garden, some of the more noxious of which are described, their habits sketched, and the means of combating them indicated. A beautiful chromo-lithograph, showing the different stages of insect metamorphosis, heads the issue, and the succeeding pages abound with well-executed illustrations. For clearness and vigor of style, the name of the author is sufficient guarantee.

book was made for use in the schools of Iowa, being limited to the physical geography and institutions of that State. This has enabled the author to give a large amount of information, locally valuable, that would be obviously out of place in a more general work. For convenience, the book is divided into two parts. Part I. gives an account of the leading natural features of the State—its physical geography, geology, climate, soil, minerals, and natural history. Part II. deals with the history of the State, and includes an account of its educational, charitable, and penal institutions. The few who may desire to carry the study into a wider field, will find the mastery of this work an excellent preparation.

author claims that books of this kind are generally too theoretical, and that he has aimed to make this especially practical. It was adopted by the educational authorities of Paris, and commended by them as a "little book which, under a modest form, contains ideas of which the popularization would be of great use—'The Practical Theory of Perspective,' a study for the use of artists, etc., by Monsieur V. Pellegrin, late Professor of Topography at the Military School of St. Cyr. The author, himself a painter, and accustomed to the manipulation of geometrical methods, was particularly qualified for writing this treatise; and he has been able, by dint of research and ability, to condense into a small number of pages the laws of perspective; and to extract, from a confused mass, rules which are very simple and easily applicable to every possible case; thus placing a sure and clear guide within the reach of all students, artists, and amateurs. Monsieur Pellegrin's excellent treatise will become a standard work."

is No. 7 of the publisher's "Science Series." The simple statement of what the author has proposed to himself to accomplish will be the best evidence of the value of this little manual. His object was to furnish to engineers a certain and ready means of ascertaining the pressures of embankments, submerged or otherwise, composed of different materials; also the moments of retaining walls, of different forms of cross-section, to successfully withstand those pressures. By having this little book at hand, the engineer will be saved the trouble of many a long calculation.

little work, which is designed particularly for the mechanical engineer, but, in a more general way, also for the civil engineer, is more indicative than instructive. That is, it points out the studies to be pursued without explaining their nature, and it tells the apprentice what work he will find in the machine-shop, without detailing the method in which it is done. It contains some practical suggestions on the