Excerpt from Rainfall of the United States: With Annual, Seasonal, and Other ChartsIt is quite probable that rain falls in the United States at one point or another every day of the year. On very rare occasions the observers of the Weather Bureau report no precipitation at a given hour, but it should be remembered that their range of vision can cover at the utmost less than one-hundredth part of the whole area.The theories of rainfall given in the books of twenty or thirty years ago are not now wholly accepted. There is one very simple principle, however, upon which no disagreement exists, viz, that in order to produce abundant rain the temperature of air must he suddenly cooled below the dew-point. When the air is thus cooled, a portion of the water vapor which is always present within it is changed to the liquid state, and that which formerly existed as a gas or vapor now becomes visible in the form of minute particles of fog or mist. The particles thus formed may ¿oat away with the wind or they may increase in size, coalesce, and fall to the ground of their own weight. Whether the condensation of vapor thus outlined results simply in cloud, or whether rain falls, depends on the magnitude of the temperature changes that take place in the air Inass whose vapor is being condensed. A rise in temperature is inimical to further condensation, a fall is favorable to precipitation.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.