Page:Popular Science Monthly Volume 39.djvu/137

Rh celestial phenomena. The old pictures of spiral nebulæ are hardly worth retaining, except for the purpose of comparison, when such photographs as those of Mr. Roberts, the Henry Brothers, and others are obtainable. An interesting feature of the illustrations retained from the preceding editions is the series of pictures of double and multiple stars. These are of material assistance to the amateur in observations of close doubles whose components can barely be separated by the highest powers of the telescope. In this edition the stars in the picture of that wonderful vari-colored cluster which Sir John Herschel discovered near Kappa Crucis, and which he compared to a casket of many-hued gems, have been represented of their proper colors, and the effect is both pleasing and instructive.

The catalogues of binary and multiple stars, and of variable, red, and temporary stars, add much to the usefulness of the volume devoted to the starry heavens.

We are acquainted with no book that contains so much practical information for the amateur about the instruments of the astronomer, their construction, and the methods of mounting and using them, as does the second volume of Mr. Chambers's work. This information ranges from the magnifying powers of different forms of eyepieces and the proper adjustment of objectglasses to the construction of observatories and the discussion of the best methods of adjusting and mounting telescopes, transit instruments, astronomical clocks, and so on. There is a great variety of practical hints and directions for the guidance of the amateur in the actual work of observation.

In view of the great development of popular interest in astronomy which the past ten years have witnessed, such a work as this must find a rapidly increasing circle of readers; and the author was probably wise in enlarging its scope, in the face of the great increase of cost involved in the change from one volume to three.

In reviewing the work of the many divisions of the Geological Survey during its ninth year, the director states that topographical surveys covering 52,062 square miles have been made by the Division of Geography. The largest areas were surveyed in Missouri, New Mexico, Virginia, Texas, and Arkansas. In Massachusetts, the survey undertaken in co-operation with the State authorities was completed. The examination of the swamp and marsh lands along the Atlantic coast south of New York was continued. These lands, "deleterious to health in their natural condition, an obstacle in the way of approach to the sea, repellent to the settler, to agriculture, and to manufactures, they yet hold out the hope of highly productive utilization through the judicious application of capital." Investigations were carried on also in many other localities, and much laboratory and office work was done. The director gives sketches of the life-work of four prominent members of the survey whose deaths occurred during the year, namely, F. V. Hayden, R. D. Irving, James Stevenson, and Thomas Hampson. Reports from the several chiefs of divisions give the details of the work in their several departments. Of the papers accompanying the director's report, the most extended one is on the Charleston earthquake of August 31, 1886, by Captain Clarence E. Dutton. The chief result obtained from this study is a close approximation to the rate at which an earthquake wave moves, and this is found to coincide with the theoretical rate. Although severe labor was expended for many months in an attempt to obtain some information respecting the cause of earthquakes, the data yielded nothing on this point. The monograph is introduced by accounts of the earthquake by three residents of Charleston who experienced it. One of these, by Mr. Carl McKinley, of the News and Courier, was prepared for the annual report of the city government. Dr. G. E. Manigault, of the Charleston College, was selected to prepare an account especially for this record, and the third was written by Mr. F. R. Fisher. The following chapters embrace detailed studies of the local effects of the earthquake and of the epicentral tracts, a summary view of the effects throughout the country, a computation of the depths of the foci, and discussions of the isoseismals, the speed of propagation through the ground of the principal vibrations, and the