Scope of this Work. --Meteorology includes the whole range of the phenomena of the air: its composition, properties, motions, and the various forms of energy manifested therein. In this work its meaning will be given fully as broad a scope. We shall include the study of those known forms of energy that, through the medium of the ether or otherwise, reach the earth from the sun; and also of those portions of the hydrosphere and the lithosphere of the earth that have to do with the absorption, the radiation, the conduction, the reflection, and the distribution of heat; and its changes of form in the processes of evaporation, condensation, and freezing.
The Aim of the Author. --The object in writing this book was to provide, so far as possible, the young men entering the service of the U. S. Weather Bureau with a comprehensive introduction to modern meteorology. But to meet their needs in this particular is to provide equally well for all others who are beginning seriously this important science.
For several years the difficulty of directing the studies of these young men has been steadily increasing. Some of the better books on meteorology were fast becoming obsolete, as must always be the case with text-books that treat of a rapidly progressing science; while others, like Hann's masterly work, were, and still are, confined to the foreign languages in which they originally appeared. An urgent necessity, therefore, for a book that would bring the essentials of meteorology up to date, in an available form, was the incentive that led to the preparation of the present work.
The fact that meteorology may be an entirely new subject to the reader has constantly been kept in mind. Technical terms therefore have been defined wherever they first occur, and an effort has been made so to discuss the subjects under consideration as to leave the student with clear and correct ideas without the use of mathematics. This plan, it is believed, will render the book of the greatest help to the largest number.
Many new features have been introduced. Among them are: