RAILROADS OF CANADA 



4921 



RAIN 



other great transcontinental Canadian lines (see 

 CANADA, subtitle Transportation). 



The Atchison, Topeka <fe Santa Fe, stretching 

 from Chicago to San Francisco and traversing 

 Kansas, Colorado, New Mexico and Arizona, 

 had in 1914 a total of 11,320 miles of track; 

 while the great Hill lines, the Northern Pacific 

 and the Great Northern, extending from Saint 

 Paul and Duluth to Portland and Seattle re- 

 spectively, possessed nearly 6,000 miles of track 

 each. The other transcontinental lines in the 

 United States are the Union Pacific ; the South- 

 ern Pacific; the Chicago, Milwaukee & Puget 

 Sound, which was deeded to the Chicago, Mil- 

 waukee & Saint Paul in 1912; and the system 

 formed by the Wabash, the Missouri Pacific, 

 the Western Pacific and the Denver & Rio 

 Grande, which runs from Denver, Colo., to San 

 Francisco. See RAILROAD. 



RAILROADS OF CANADA. 1 * See article 

 CANADA, subtitle Transportation. 



RAIN. Shakespeare, in The Merchant of 

 V' nice, has a beautiful description of the 

 quality of mercy, which he says is like the 

 "gentle rain from heaven." Probably no phe- 

 nomenon in nature has received more grateful 

 tributes than the fall of rain, because upon it 

 depend the comfort and happiness of mankind. 

 This idea is expressed picturesquely in these 

 lines of an old poem: 



The pastures lie baked, and the furrow is bare. 

 j The wells they yawn empty and dry ; 

 But a rushing of waters is heard In the air, 



And a rainbow leaps out in the sky. 

 Hark ! the heavy drops pelting the sycamore 



lea\ 



How they wash the wide pavement, and sweep 

 from the eaves. 



And deep in the fir-wood below, near the plain, 



A single thrush pipes full and sweet, 

 How days of cle.ir shining will come after rain, 



Waving meadows, and thick-growing wheat ; 

 So the voice of Hope sings, at the heart of our 



fears. 

 Of the harvest that springs from a great nation's 



tears: 

 O. the rain, the plentiful rain ! 



What Is Rain? A child asked this question 

 would probably say that rain is water that falls 

 out of clouds in drops. Such an answer would 

 be correct, though it does not explain why the 

 clouds form or why they lose their moisture, 

 formation of rain depends upon several in- 

 teresting processes in nature. Moisture is con- 

 stantly bring takm up into the air from tin- 

 It's surface, particularly the warmer parts 

 l>e ocean, by a process called evaporation. 

 This moisture, called water vapor, is invisible; 



it is mingled with the other gases in the air and 

 is carried about by the winds. When the 

 moisture-laden air is cooled to a certain point 

 the vapor it contains condenses into tiny parti- 

 cles of water so fine that they might be called 

 water dust. This water dust is known as cloud 

 or fog, according to whether it is high in the 

 air or near or at the surface of the earth. A 

 further cooling of the air will cause the minute 

 cloud particles to condense and unite into drops 

 so large and heavy that they fall by their own 

 weight. Floating dust motes in the air have 

 something to do with rain formation, for 

 tiny dust particles form lodging places for the 

 condensing vapor, and, because they cool more 

 rapidly than the air, they hasten the condens- 

 ing process. The essential condition, however, 

 is the reduction of the temperature to a point 

 where the air can no longer hold the moisture 

 it contains. When the air contains all the 

 vapor that jt can hold at a certain temperature 

 , it is said to be saturated, or at the dew point. 

 Rain occurs when the temperature falls below 

 the dew point. 



Raindrops and Their Work. Probably every 

 one has observed that raindrops vary greatly in 

 size and in the swiftness with which they de- 

 scend to the earth. The largest drops that have 

 been measured were about one-fourth of an 

 inch in diameter and traveled at the rate of 

 from fifteen to twenty-five feet a second. The 

 smallest drops measured were not more than 

 one-twentieth of an inch in diameter and foil 

 at a much slower rate, probably about five feet 

 a second. Raindrops, in falling, wa^h all sorts 

 of impurities out of the air dust, soot, pollen 

 from plants, and many other solid substances. 

 It has been calculated that a five days' rain 

 in London, England, which is a very smoky, 

 dirty city, will wash from the air 3,738 tons of 

 solid impurities, including 267 tons of sul] 

 of ammonia and 2,000 tons of soot and other 

 suspended matter. 



Why and Where Rainfall Varies. It has al- 

 ready been stated that a great amount of i 

 turo is evaporation from the warmer parts of 

 the ocean. Consequently tropical regions 1 

 in general, n very heavy rainfall. A yearly 

 i UK) inches of rain might be given for 

 the tropics, om-thu-.l as much for the temper- 

 ate zones, an<i h as much for the polar 

 regions. The actual variation, however, is far 

 greater than this. Tin- highest rainfall rvrr re- 

 corded for one year was 805 inches, in Assam, 

 India; the lowest was three one-hundredths of 

 an inch, in Walfish Bay, on the west coast of 



