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<h2>CHAPTER XX.</h2> 416. What is rain? Rain is the vapour of the clouds which, being condensed by a fall of temperature, forms drops of water that descend to the earth. It is the return to the earth in the form of water, of the moisture absorbed by the air in the form of vapour. 417. Does rain ever occur without clouds? It sometimes, but rarely happens, that a sudden transition from [Pg 101] warmth to cold will precipitate the moisture of the air, without the formation of visible clouds. <hr class="bible-verse" /> "Canst thou lift up thy voice to the clouds, that abundance of waters may cover thee?"—Job xxxviii. <hr class="bible-verse" /> 418. Why are drops of rain sometimes large and at other times small? Because the drops, in falling, meet and unite, and also gather moisture in their descent. The greater the height from which a rain drop has descended, the larger it is, provided that its whole course lay through a rainy atmosphere. The size of the drops is also influenced by the amount of moisture in the atmosphere, the degree of cold, and the rapidity of the change of temperature, by which the drops are produced. 419. In what seasons of the year are rains most prevalent? Throughout Central Europe rains are most prevalent in summer, but in Southern Europe the preponderance is on the side of winter rains. 420. In what months of the year does it rain most frequently in this country? It rains more frequently from September to March, than from March to September; but the heaviest rains occur from March to September. 421. Why are there more rainy days from September to March? Because the temperature of the air is more frequently lowered to that degree which precipitates its vapours. Months in the order of their comparative wetness:—1. October. 2. February. 3. July. 4. September. 5. January. 6. December. Months in the order of their comparative dryness:—1. March. 2. January. 3. May. 4. August. 5. April. 6. November. 422. In what part of the world does the greatest quantity of rain fall? The greatest quantity of rain falls near the equator, and the amount decreases towards the poles. [Pg 102] <hr class="bible-verse" /> "Who can number the clouds in wisdom? or who can stay the bottles of heaven."—Job xxxviii. <hr class="bible-verse" /> 423. In what part of the world do the heaviest rains occur? The heaviest rains occur in the tropics, during the hot season. The drops of rain in the tropical regions are so large, and the force with which they descend so great, that their splash upon the skin causes a smarting sensation. 424. In what parts of the world do the least rains occur? There are some parts of the earth which are rainless, such as Egypt, the desert of Sahara, the table lands of Persia and Montgolia, the rocky flat of Arabia Petræ, &c. 425. How many rainy days are there in a year? The frequency of rainy days is greatest in countries near the sea, and their number decreases the further we journey from the sea-border towards the inland. In England it rains on an average 152 to 155 days in the year. 426. In what part of England does the greatest amount of rain fall? In the town of Keswick, in Cumberland, where 63 inches of rain fall in a year; Kendal, in Westmoreland, 58 inches; Liverpool, 34 inches; Dublin, 25 inches; Lincoln, 24 inches; London, 21 inches. 427. Why do the heaviest rains occur at the tropics? Because the hot air absorbs a large amount of vapour, and rises into the higher regions of the atmosphere, where the vapours are suddenly condensed into heavy rains, by cold currents from the poles. 428. Why does the greatest quantity of rain fall at the equator? Because the hot air absorbs a large amount of vapour, and as the atmosphere is usually calm, there is an absence of currents, by which the saturated air would be removed. In this, which is called "the Region of Calms," rain falls almost daily. 429. Why are some parts of the earth rainless? [Pg 103] Because, being situated in tropical or torrid latitudes, and at a distance from the ocean, the atmosphere above them is always in a dry state. <hr class="bible-verse" /> "Thou, O God, didst send a plentiful rain, whereby thou didst confirm thine inheritance, when it was weary."—Psalm lxviii. <hr class="bible-verse" /> 430. When is air said to be saturated with vapour? When it cannot take up a larger quantity than that which it already holds. When common salt is dissolved in water, until the water can take up no more, the water is then said to be saturated with salt. 431. What proportion of water is air capable of sustaining in the form of vapour? The amount of water held in suspension by the air averages the following proportion: one thousand cubic feet of air contain as much vapour as, were it condensed to water, would yield about two fifths of a pint. But one thousand cubic feet of air are capable of holding half-a-pint of water; and this may be regarded as the point of saturation. Thus, in a room ten feet square and ten feet high, the air, at the point of saturation, would hold in the form of vapour, half-a-pint of water. It must not be forgotten, however, that the point of saturation necessarily varies with the temperature of the air. 432. Why are cloudy days and nights not always wet? Because the air has not reached the state of saturation. 433. Why does rain purify the air? Because it produces motion in the particles of the air, by which they are intermixed. And it precipitates noxious vapours, and cleanses the face of the earth from unhealthy accumulations. 434. Why are mountainous localities more rainy than flat ones? Because the mountains attract the clouds; and because the clouds that are flying low are borne against the sides of the mountains and directed upwards, where they meet with cold currents of air. 435. Why does more rain fall by night than by day? [Pg 104] Because by night the temperature of the air, heated during the day, falls to that degree which condenses its vapours into rain. <hr class="bible-verse" /> "As the hart panteth after the water brooks, so panteth my soul after thee O God."—Psalm xlii. <hr class="bible-verse" /> 436. Why do bunches of dried sea-weed indicate the probability of coming rain? Because they readily imbibe moisture, and when they become soft and damp they show that the air is approaching the point of saturation. 437. Why does the weather-toy, called the "weather-cock," foretell the probability of rain? Because it is made with a piece of cat-gut which swells with moisture, and as it swells, shrinks. The cat-gut is so applied that when it shrinks, it turns a rod which sends the man out of the house, and when it dries it sends the woman out. Therefore, when the man appears, it is a sign of wet, and when the woman appears it is a sign of dry weather. There is another toy, called the Capuchin, which is made upon the same principle. The figure lifts a hood over its head when wet is approaching, and takes it off when the weather is becoming dry. In this case, a piece of cat-gut is also employed. Various weather-toys may be made upon this principle—among others, a little umbrella, which will open on the approach of wet, and close on the return of fine weather. A gentleman once made a wooden horse, which he declared should of itself walk across a room, without machinery of any kind. The assertion was discredited; but the horse was placed in a room close to the wall on one side. The room was locked, and otherwise fastened, so that no one could interfere with the experiment. After a time the door was opened, and it was found that the horse had actually crossed the floor, and stood on the opposite side. The horse was made from wood of a peculiar kind, liable to great expansion in wet weather, and cut in a manner to produce the greatest elongation. The fore hoofs were so made that where they were set they would remain, so that the contracting parts should draw up from behind. It is easy to understand how, in this way, the wooden horse crossed the apartment. 438. Why does ladies' hair drop out of curl upon the approach of damp weather? Because the hair absorbs moisture, which causes its spirals to relax and unfold. 439. Why is it said in mountainous countries that rain is [Pg 105] coming, because the mountains are "putting their night-caps on?" Because the clouds descend when they are heavy with vapour, and being attracted to the mountain tops they are said to "cap the mountains." <hr class="bible-verse" /> "Hast thou entered into the treasures of the snow; or hast thou seen the treasures of the hail."—Job xxxviii. <hr class="bible-verse" /> <hr class="chap" /> <div style="break-after:column;"></div>

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