504 SCIENCE OF HOME AND COMMUNITY 



boats ; and in this way many dollars' worth of property 

 and many lives are saved. A single storm warning has 

 been known to keep in port vessels and cargoes valued at 

 $30,000,000. 



Protection from floods. When floods are threatening on 

 account of heavy rains, warnings are sent to the people 

 living along the banks of rivers. In 1912 the Weather 

 Bureau sent warnings to the people living along the Missis- 

 sippi River that there was to be a severe flood. As a result, 

 the people living near the river were able to remove their cattle 

 and other property and the freight at the wharves to a place 

 of safety. It was estimated that property to the value of 

 $61,000,000 was thus saved. 



It is estimated that the total value of the property saved 

 each year through the warnings issued by the Weather 

 Bureau is $30,000,000. 



Besides the saving of lives and property thus effected, 

 the weather forecasts made by the Bureau and printed in 

 the daily papers are of some value to people in making their 

 plans. 



How is the Weather Bureau able to make these forecasts 

 of weather so as to foretell frosts, storms, floods, and gen- 

 eral weather conditions? This is done by means of the 

 weather map. In order to understand the method of using 

 it, we will look at the map shown in figure 199. 



Description of weather map. Two sets of lines arranged 

 in irregular curves are found on the map, the solid lines and 

 the broken lines. The solid lines show the air pressure and 

 are called isobars. They are marked in tenths of an inch. 

 The line marked 30.2 means that all the places through which 

 this passes have a pressure of 30.2 inches. These are made 

 for every tenth of an inch. Two kinds of areas are found on 

 the map, " high " and " low." This refers to the air pres- 

 sure. In general a low area, called a cyclone, is accompanied 

 by clouds, precipitation, and warmer temperatures. The 



