Page:Popular Science Monthly Volume 2.djvu/212

 to ascertain. Different localities would no doubt require a different proportion. Rentzsch (quoted by Marsh) estimates that for the interior of Germany about 23 per cent., and along the coast 20 per cent., is necessary for the needed protection. The case hardly admits of such precision; more would no doubt be better, and in a dry climate like ours, more than anywhere else.

So rapidly is the destruction of timber going on in this country that many localities originally covered with forest have not so great a proportion as this remaining, and other localities are in a fair way soon to be in the same condition. This is becoming, or at least should become, a real cause of apprehension to those who have the welfare of the farming interest, and especially of the fruit-growing interest, at heart. This continuous destruction of timber must eventually result in injury to the market value of lands in certain neighborhoods, especially lands for fruit-growing purposes.

The remnants of forests in the States have another enemy as inexorable and remorseless as the woodman's axe. Many forest-trees, like the wild Indian, do not seem to flourish in the midst of civilization. They first show signs of decay at the top. This takes place after the underbrush has been cleared away and the surface has lost that perfect mulch of decayed leaves which belongs to native forests. The trees are now liable to suffer from extremes of drought as never before. This change is equal to a change of habitat, and the consequence to some varieties of trees is loss of health and vitality.

According to the experiments of Prof. Pfaff made on an oak-tree, the amount of moisture lost by transpiration during the summer-season was more than eight times the quantity of rainfall on the same area for the same time. Dr. Hahn, who thinks this estimate quite too high, says, nevertheless, that "Herr Pfaff's results show us what an enormous quantity of water is required by isolated trees in a comparatively dry and free (bewegten) atmosphere, and how much they need the protection which they afford to each other in their combined capacity as a forest." Whenever the balance and integrity of the original forest is broken, the supply of water during droughts not being equal to the demand of trees now suffering the double disadvantage of needing more moisture and less of it available than before, death begins in the topmost branches, that part of the tree which is most exposed to the conditions of active transpiration and farthest removed from the source of moisture.

What should we do about this blight? Save the timber by using it before it is injured, and plant enough to make up for the loss.

For the application of the facts as now ascertained, let us take the southern shore of Lake Erie, which is a good fruit-region lying midway between the Eastern and Western cities, and affording to both part of their supply of fruit. Fruit does not do so well here now as it did in the early settlement of the country. Cut off the timber which still