250 THE WEATHER 



reau, is especially needed hi the United States, owing to the 

 great range of the country in latitude and longitude, and 

 the great variety of its weather conditions. The Bureau 

 is a part of the Department of Agriculture. 



Many trained observers gather the weather conditions 

 each day, at 8 A. M. on the Atlantic coast and at 5 A. M. 

 on the Pacific. When their reports are telegraphed to 

 Washington, they give an instantaneous photograph of 

 the weather of the whole country. The facts reported by 

 the observers are simply the barometer height, tempera- 

 ture, rainfall or snowfall, direction and velocity of the 

 wind, etc. But the combined results, when placed upon 

 a map, make it possible for the expert at Washington not 

 only to tell what the weather is, but what it is likely to 

 be. Thus the coming of cold waves, of storms that are 

 likely to injure ships, of floods upon rivers, all can be fore- 

 told with more or less accuracy. That some forecasts 

 fail does not mean that the Weather Service is at fault, 

 but that all storms are not alike. But the forecasts 

 actually save to the people not only many lives, but 

 millions of dollars' worth of property annually: many 

 times the cost of the service. 



The case of the Mississippi floods illustrates how the Service works. 

 If there are heavy rains in the Upper Mississippi Valley, there will be 

 serious floods along the lower course of the river. The "weather 

 man" knows the rainfall, and how much the river can carry off in an 

 hour; hence he knows what chance the river has of carrying all the 

 water it will receive. If more water is poured into it that it can carry, 

 the level of the river must go up. The greatest floods of recent years 

 have occurred in 1897, 1903, 1912, and 1913. In the flood of 1912 the 

 Bureau predicted that the crest, or highest part, of the flood would 

 reach 54 feet at Cairo, 46 feet at Memphis, 53 feet at Vicksburg, 42 



