Take your map of North America and note, in this respect, its peculiarities. It extends from the Isthmus of Darien to the Arctic regions, and from the 65th to the 160th meridian of west longitude from Greenwich, and has upon its surface a type of every climate in the world. For the purpose of simplifying and illustrating the matter in hand, let us divide it into five sections. Let the first section embrace Central America and Southern Mexico, south of 28 deg.; the second, Northern Mexico and Southern New Mexico, California, etc., between the parallels of 28 deg. and 32 deg.; the third, Northern California, Utah, Southern Oregon, and Western New Mexico, north of the parallel of 32 deg.; the fourth, the entire continent north of 42 deg.; and the fifth, the eastern United States, east of the meridian of 100 deg.. These divisions are not intended to be entirely accurate in their separation, but substantially so for the purpose of illustrating the differences which exist in each. The accompanying diagram shows approximately, by dotted lines, the divisions. [Illustration: Fig. 2.] Now let us see in what a diverse manner, and to what a different extent, they are severally supplied with moisture. Central America and Southern Mexico lie within the tropics--their rains are tropical rains. The season is divided into wet and dry, as are the seasons of all tropical countries which are not rainless. During the rainy season it rains a portion of nearly every day, and during the dry season the sky is clear, the air is pure, and rain seldom falls.