14 



the tropical countries with the heavy rains that Ml over them. Our readers are 

 most fomiliar with them as the rains of Central America. They fall as this 

 machinery is carried northward with the sun, and as it returns to the south. 

 Hence, except at its extreme northern and southern limits, this rainy belt an- 

 nually passes twice over the same country. As the sun recedes south from the 

 tropic of Cancer the extra tropical-region becomes larger, for it moves south with 

 the sun. When the latter has reached the tropic of Capricorn, the line between 

 the trade-wind belt and the extra-tropical is about the thirty-second degree of 

 latitude. The rainy belt, when it has reached its furthest northern point, ex- 

 tends only to the twenty-eighth degree. Hence no rain ever falls between the 

 twenty-eighth and thirty-second degrees of latitude. These portions of the 

 world, both of north and south latitude, are always dry. The Peruvian guano 

 islands lie in one of them, and hence the vast accumulations of this rich manure, 

 for a few rains would soon cause its decay. 



This rainless belt of land commences its eastern limit at the western settle- 

 ments of Texas, thence passes through the northern half of Chihuahua, Sonora, 

 and Lower California. JMr. Bartlett says of it : " Here shrubs and trees disap- 

 pear, except the thorny chapparal of the deserts ; the watercourses all cease, 

 nor does any stream intervene until the Rio Grande is reached. This great 

 desert region extends over a district eraliracing sixteen degrees of longitude, or 

 about a thousand miles, and is wholly unfit for agriculture. It is a desolate, 

 barren waste, which can never be rendered useful for man or beast, save for a 

 public highway.'' 



Turning to the first plate, it will be seen that on the eastern part of North 

 America and of Asia, the rainy belt and the extra-tropical region are united. 

 The light-colored belt of the northern trade-wind is in these places darlcened, 

 indicating that showers cover them whilst all other parts under the trade-winds 

 are dry. Why is this? The answer, as given by Mr. Butler, is, that the 

 mountains of Central America being higher than the rainy belt, are, by the rota- 

 tion of the earth eastward, as well as by their greater height, forced against the 

 rainy belt which moves westward, thus acting as a dam against it. There re- 

 sults an accumulation of this aerial belt; and as the mountains run from the south- 

 east to the northwest, the accumulated belt flows towards the northwest, until, 

 mingling with the iipper or counter trade, it follows its course, curving round 

 to the northeast. This overflow extends northwards as the sun advances in the 

 same direction. The following map shows the portion of the Atlantic States 

 covered by it about the first of February, reaching nearly as far north as the 

 mouth of the Ohio river. 



