Page:Popular Science Monthly Volume 67.djvu/691

Rh the extent of losses by methods still in vogue, the author concludes: "A comparison of the duties secured. . . leads to the belief that it will be possible through improved methods to double the average duty now obtained, so that the quantity now required for one acre will serve to irrigate two. If this can be accomplished it will relieve the scarcity under many canals, put an end to many controversies growing out of such scarcity, lessen the expense per acre for water and immensely increase the productive and taxable resources of the arid states."

In various parts of the old world, where much valuable land has been reclaimed by irrigation, water is distributed in such a way as to secure the best practicable results. At Biskra, Algeria, for example, where the famous Deglet Noor date is grown and the supply of water is limited, an excavation is made around the base of each tree, and this is filled with water, thus greatly lessening the loss that would otherwise result from evaporation, At Bassorah, on the river separating Persia from Arabia, the extensive date plantations are watered by means of a system of canals which are flooded with each high tide, dams of mud being built with the hollow trunks of palms run through them, which permit the water forced into the canals by the rising tide to flow away slowly. Thus, by taking advantage of favorable natural conditions, an ideal system of combined irrigation and drainage is effected at a minimum' of expense.

In close agreement with the estimates of Dr. Mead, observations of the writer have shown that plants supplied with water below the surface of the ground have made a vigorous growth on a little more than one half the quantity of water that would be required if applied at the surface. To report a single rather striking case—the plants shown in the accompanying figure are photographs of seedlings of palo verde (Parkinsonia, two species) which, with some other desert plants, were under investigation. They are here shown as they appeared August 10, after being supplied with measured quantities of water since June 12. During this period numbers 1 and 2 each received 71 ounces of water, while numbers 3 and 4 each received but 39 ounces, or 55 per cent, as much as 1 and 2. Numbers 1 and 3