arresting and consuming those countless meteoric stones, showered upon us from stellar space, before they can penetrate to the lower aerial strata. For us, at least, in respect to this sublunary scene, it is of engrossing interest, as that all-pervading organism which
"Lives through all life, extends through all extent,
Spreads undivided, operates unspent."
In the technical execution of this purely pioneer work, the first step was the preparation of a daily graphic and synoptic chart exhibiting all the weather observations taken simultaneously in the northern hemisphere. On the 1st of July, 1878, the Signal-Office at Washington began the regular publication of a daily international weather-map, charted daily and issued daily, each chart being based upon the data appearing in the "International Bulletin of Simultaneous Reports" of similar date. The daily issue of a weather-chart of this kind and scope is without a precedent in history. It illustrates the cooperation, for a single purpose, of the civilized powers of the globe north of the equator, and brings the atmospheric phenomena over the whole field of the research, and in their true relations to each other, within the easy comprehension of the student's eye. (See frontispiece.) As these charts in successive order are spread out day after day, the investigator has before him a vivid panorama of the physical forces in pictured action, so that he can readily trace their mutual dependence and interaction in the normal working of the ponderous, yet beautiful, atmospheric machinery.
The history of progress in the discovery of physical phenomena and their laws is intimately connected with the introduction of technical contrivances so simple that at first they attract little notice. After the invention of the mariner's compass, and the astrolabe, nothing perhaps that was done for geographical science gave it such an impulse as the chart introduced in 1556 by Gérard Mercator, by which the earth's entire surface was presented in a single picture to the geographer's eye, and by which (the degrees of latitude and longitude at all places bearing to each other the same relations they bear on the sphere itself) the navigator could readily steer his ship in straight lines. This simplest of contrivances became, in a word, an invaluable instrument of maritime exploration and discovery, the present and almost exclusive employment of which by mariners of all nations, as the chart for the ocean, has brought the name of Mercator down to this day in honored remembrance. Not to dwell upon the charts of Paolo Toscanelli in the fifteenth, and of Martin Behaim in the sixteenth century, so justly celebrated--the former as guiding Columbus on his great west-ward voyage, and the latter as blazing Magellan's perilous way toward the southern shore of South America, to circumnavigate the globe--we may well say, "Accurate maps are the basis of all inquiry conducted on scientific principles." The "International Weather-Map of Simulta-
