:
to utilize, to summarize, catastrophic, automatic, nomic, experimental, economically, automation, accumulation, section, capital, computer, optimal, optimum
11. , , :
to overestimate, to misuse, humidity, density, useless, doubtless, improper, inadequate, particularly, successful
III. :
1) , :
to compute, to consume, to erode, to move, to accumulate, to restore, to require, to reclaim, to demand, to drain, to dispose, to pump, to use, to experiment, to insta11, to grow
2) , :
maintenance, storage, delivery, performance, reclamation,
division, elimination, disposal, selection
IV , . drainage:
efficient, complete, adequate, arid, proper, humid, successful, expensive, automatic, convenient, normal, favorable
V. , . , .
Vl. , .
Vll. Drainage.
VIII. . , :
8. Who Demands Purer Water?
Since rain-water is very good for plants, and sea-water is very bad, we may ask whether there is some intermediate kind of water that the p1ant wil1 just tolerate. The question is likely to be of great importance in arid regions where the only available irrigation water comes from underground sources. During its long staying and slow movement deep below the surface, the water dissolves minerals' salts from the rocks that surround it. Suppose this mineralized water is now offered to (1) human beings, (2) animals, (3) food-plants, and (4) machines; how will they respond?
n wil1 drink water containing 1 part in 1,000 of dissolved salt, animals wi11 drink water that is much more saline, while food-plants demand purer water.
This is not only because the salt is harmful to the plant but mostly due to the fact that after long periods, the land irrigated with saline water becomes saturated with salt and in the end becomes unfit for cultivation. The water itself drains away or is transpired and the salt stays in the ground. The irrigation water should not be more than about one fifteenth as salt as sea water, its mineral content should be much less than 1 part in 1,000. But if the local climate and the nature of the ground are favorable, some plants will grow on water that is much more saline than this.
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The Use of Solar Energy
The Sun possesses a limitless amount of energy and mankind is looking for different ways to uti1ize it because time will come when we shall not have any other energy but the Sun's. Coal, oil and gas will be used up.
The most primitive device for using the heat of the Sun is the gardener's greenhouse. Usually this device consists of the solar water-heater placed on the roof of the greenhouse and covered with g1ass. The water circulating in it is heated by the Sun, then pumped into a hot-water tank warming the greenhouse. Such a 100 square-metre greenhouse was built in Turkmenia: solar energy is used to grow flowers and vegetab1es all the year round on a commercial basis.
Solar energy is used both for heating houses and for cooling them. For example in Florida many "solar houses" have been built. In these houses some material is used to take it and to keep heat of the Sun and to give it away gradually as required. Water is a good material for the purpose, but Glauber's salt is even more efficient. It melts at atemperature of 90' talking in a large amount of heat which it gives back when it turns into crystals again. Another interesting material is gravel in the walls of the house, which it keeps warm on sunless days. In Ashkhabad there are many houses cooled with the help of solar energy. Ten children's institutions in the same city have been equipped with showers. They look like any other showers, except that water for them is heated by the Sun to a temperature of 70' C on the south sides of the houses. As Turkmenia gets more than 180 sunny days each year (as many as Egypt and California) solar showers can be used from early spring till late autumn.
