We see now that our climate is the product of many factors. It frequently varies greatly in places only a few miles distant from each other. Consequently there may be a great variety of productions and industries in one small area, while in other regions the climate and productions are almost unchanged for hundreds of miles. SOMETHING ABOUT IRRIGATION Travellers from the Eastern States who visit New Mexico for the first time are attracted by many unusual sights. There are the interesting little donkeys, the low adobe houses of the native Mexicans, and the water ditches winding through the gardens and fields, which are divided into squares by low ridges of earth. If the fields are seen in the winter time, when dry and barren, the meaning of their checkered appearance is not at first clear, but in the spring and summer one is not long in finding out all about them. When the time comes to sow the seed, water is turned into these squares from the ditches which traverse the valleys, and one square at a time is filled until the ground in each is thoroughly soaked. Afterward, when the ground has dried enough to be easily worked, the crop is put in. The seeds soon sprout under the influence of the warm sun, and the land becomes green with growing plants. The same method of moistening the ground is used for the orchards and vineyards. What is the use of all this work? Why not wait for the rains to come and wet the earth, as the farmer does in the eastern United States? The Mexicans, who have tilled these valleys for more than two hundred years, ought certainly to have learned in all that time how to get the best returns. You may be sure that they would not water the ground in this way if it were not necessary. The fact is that over a large portion of the western half of the United States it does not rain enough to enable the farmer to grow his crops. The climate is generally very different from that of the Middle and Eastern States. When the Mexicans moved northward into the valley of the Rio Grande River, into Arizona and California, they found a climate similar in many respects to that at home, and soon learned that it was necessary to water the land artificially in order to make it productive. Though in many places sufficient rain fell, yet the heaviest rainfall came in the late summer or winter, when the plants needed it less, while the spring and summer were long and dry. The Mexicans were not the first to practise watering the land, if we may judge from the ruins of ancient ditches constructed by the primitive Indian inhabitants. It is evident that they too made use of water in this manner for the growing of their corn and squashes. This turning of water upon the land to make it productive is termed "irrigation." The work is performed in different ways, as we shall see later. Irrigation is now carried on through all portions of the United States where the rainfall is light and streams of water are available.