. The elements of forestry, designed to afford information concerning the planting and care of forest trees for ornament or profit and giving suggestions upon the creation and care of woodlands with the view of securing the greatest benefit for the longest time, particularly adapted to the wants and conditions of the United States. Forests and forestry. Effect of Forests upon Balnfall and Temperature, 21. W4W-^^fy 9. Lysimeter. Belation between the Ramjall and the Native Forests. 85. As a general rule, we find our native forests more dense in proportion as the rainfall is greatest, as we see p
. The elements of forestry, designed to afford information concerning the planting and care of forest trees for ornament or profit and giving suggestions upon the creation and care of woodlands with the view of securing the greatest benefit for the longest time, particularly adapted to the wants and conditions of the United States. Forests and forestry. Effect of Forests upon Balnfall and Temperature, 21. W4W-^^fy 9. Lysimeter. Belation between the Ramjall and the Native Forests. 85. As a general rule, we find our native forests more dense in proportion as the rainfall is greatest, as we see proved upon the Pacific Coast, and in the region south of Lake Supe- rior. They become less as the rains diminish, and as we approach the great plains, the native timber is found only along the borders of the rivers and smaller streams, and finally it disap- pears altogether. Asa rule, where the amount of rain is less than twenty inches in a year, and this chiefly in winter, the growth of trees becomes difficult, and with many species impos- sible. 86. There is some reason to believe that the capacity for cultivation in a dry region may be increased by tree-planting, and gradually extended to a degree that would not be possible to secure at first. Effect of Woodlands upon the Temperature of the Air and the Earth. 87. It is evident to the senses that the air in woodlands is cooler than in the open fields in summer and warmer in winter, although the actual difference in the latter is slight. When we measure the temperature of the soil, we find the effect of woodlands much greater, the difference between winter and summer being less in the woods than in the fields, and less at greater depths than at the surface. This difference is greatest in summer, when vegetation is most active. Various means are employed to measure this temperature. In one, a thermometer with a thick glass bulb (invented by Lamont, of Munich), is left to various depths, and when drawn up for observation it does
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