It is with a feeling of increased responsibility, shared doubtless by the Presidents of other sections, that the Vice-President of the Geography of the Air brings before you his modest annual contribution in one branch of geographical science.
We live in an age so imbued with earnest thought, and so characterized by patient investigation, that an eager gleaner in scientific fields finds at the very outset his mind filled with the garnered grain of golden facts. The more cautious searcher often follows with uncertain mind, and doubtless in his backward glances sees many fairer and heavier sheaves than those he bears with full arms, from the fruitful harvest. If, then, you do not find here dwelt on such geographical phases as you judge most important, attribute the fact I pray you, not to neglect, but to lack of observation, or to the exercise of an undiscriminating judgment.
First let us turn to the higher class of investigations, wherein that handmaid of science, a true and noble imagination, comes to supplement exact knowledge, to round out and give full form and perfect outline, either shaping a number of disjointed and apparently heterogeneous facts into a harmonious series, or evolving from a mass of confusing and seemingly inexplicable phenomena a theory or law consistent therewith.
In this domain Professor Ferrel's book on Winds is probably the most important theoretical meteorological discussion of the past year. It owes its value to the fact that it puts into comparatively simple and popular form the processes and results of his intricate mathematical investigations of the motions of the air, published by him years since, and later elaborated during his service with the Signal Office.
In connection with the subject of winds, Professor William M. Davis has formulated an excellent classification, depending first, on the ultimate source of the energy causing the motion; second, on temperature contrasts which produce and maintain winds; and third, on their periodicity and the time of the first appearance of the motion.
Professor Russell, appropriately it seems to me, remarks regarding the landslide winds, that avalanche would be a better term than landslide as applied to winds associated with fallen masses of earth or snow.
With the enormous amounts of accumulated tabulated matter, and numerous studies bearing on isolated meteorological phenomena, it is a specially important consideration that some students pay constant attention to the investigations of the laws of storms. From such researches definite advances in theoretical meteorology may be made and fixed laws determined, which may be of practical utility with reference to the better forecasting of the weather. In the United States Signal Office, Professor Abbe has brought together the results of his studies and investigations for the past thirty years, under the title, "Preparatory studies for Deductive Methods in Storm and Weather Predictions." This report will appear as an appendix to the annual report of the Chief Signal Officer of the army. Professor Abbe finds that the source and maintaining power of storms depend on the absorption by clouds of solar heat, and in the liberation of heat in the cloud during the subsequent precipitation, which, as he endeavors to show, principally influences the movement of the storm-centre.
In this method one takes a chart showing current meteorological conditions, and the permanent orographic features of the continent; lines of equal density are also drawn for planes at several elevations above sea-level. On these latter, and on the lines of the orographic resistance, are based intermediate lines of flow, which show where conditions are favorable to cooling and condensation. The amount of condensation and its character, whether rain or snow, are estimated by the help of the graphic diagram. Numbers are thus furnished that can be entered on the chart and show at once the character of the new centre of buoyancy, or the directions and velocity of progress of the centre of the indraft and the consequent low barometer.
It is hoped that this work of Professor Abbe's may be, as he anticipates, of great practical as well as theoretical value. Steps are being taken to test the theoretical scheme by practical and exhaustive applications to current work.
Tiesserenc de Bort has continued his work, of improving weather forecasts for France, by studying the distribution of the great and important centres of high pressures, which prevail generally over the middle Atlantic ocean, and, at certain periods of the year, over Asia, Europe, and North America. His studies have proceeded on the theory that the displacements of centres of high pressure, whether in Asia, over the Azores, near Bermuda, in North America, or in the Polar regions, set up a series of secondary displacements, which necessarily cause storm centres to follow certain routes. M. de Bort concludes that a daily knowledge of the relation of these centres and their areas of displacement will eventually enable skilled meteorologists to deduce the position of unknown and secondary centres. He has endeavored to reduce these various displacements to a series of types and has made very considerable progress in this classification. Daily charts covering many years of observations have been prepared, and these separated, whenever the characteristics are sufficiently pronounced, into corresponding types. This plan of forecasting necessitates extended meteorological information daily, which France obtains not only from Russia, Algeria, Italy and Great Britain, but, through the coöperation of United States, from North America. The daily information sent by the Signal Office shows, in addition to the general weather over the United States and Canada, the conditions on the western half of the North Atlantic ocean, as determined by observations made on the great steamships, and furnished voluntarily by their officers to the Signal Office through the Hydrographic Office and the New York Herald weather bureau.