WEATHER BUREAU. 53 



be expected to prevail during the following thirty-six to forty- 

 eight hours. A complete telegraphic report includes the follow- 

 ing data: temperature, pressure (reduced to sea level), precipi- 

 tation, direction of wind, state of weather, current wind velocity, 

 maximum and minimum temperature since last observation, and 

 kind and amount of clouds with the direction of their movement. 

 From these data the forecaster by comparison with preceding 

 reports is able to trace the paths of storm areas from the time 

 of their appearance to the moment of observation and approxi- 

 mately determine and forecast their subsequent courses and the 

 occurrence of other weather conditions. 



It is a wonderful picture of atmospheric conditions that is 

 presented twice daily to the trained eye of the weather forecaster. 

 It embraces an area extending from the Atlantic to the Pacific, 

 from the north coast of South America over Mexico, the islands 

 of the West Indies and the Bahamas, northward to the uttermost 

 confines of Canadian habitation. It is a panoramic picture of 

 the exact air conditions over this broad area. Their develop- 

 ment since last report is noted and from the knowledge thus 

 gained their future course and intensity is quite successfully 

 forecast. Every twelve hours, the kaleidoscope changes and a 

 new graphic picture of weather conditions is shown. Nowhere 

 else in the world can meteorologists find such an opportunity to 

 study storms and atmospheric changes. 



The system for the collection of telegraphic reports of obser- 

 vations is so arranged that all of the principal stations in the 

 United States receive reports from a sufficient number of other 

 stations to represent the general weather conditions over a con- 

 siderable portion of the country. Forecast centers are also estab- 

 lished at Boston, Chicago, New Orleans, Denver, San Francisco, 

 and Portland, Ore. 



Within two hours after the morning observations have been 

 taken the forecasts are telegraphed from the forecast centers 

 to about one thousand principal distributing points, whence they 

 are further disseminated by telegraph, telephone, and mail ; in 

 this manner the forecasts reach about 80,000 addresses daily; 

 the greater part being delivered early in the day, none later, as 

 a rule, than 6.00 P. M. of the day of issue. This system of fore- 

 cast distribution is wholly under the supervision and at the 

 expense of the government and is in addition to and distinct 



