774 The Outline of Science 



RECORDING METHODS 



The Organisation of a Meteorological Service 



In countries possessing an official meteorological service the 

 general plan adopted is that of a central office where the fore- 

 casts are prepared and issued and the statistics dealt with, and 

 with this central office there is associated a large number of 

 "observatories," "telegraphic recording stations," and "climatolo- 

 gical stations," all of which deal in greater or less detail with the 

 recording of the meteorological elements. The observatories and 

 telegraphic reporting stations take simultaneous observations at 

 certain definite hours, and transmit these observations immedi- 

 ately in code by telegraph to the central office, where all the 

 observations so made are plotted upon a map of the country, and 

 from the map so drawn certain inferences as to the probable 

 course of the weather are made by the staff whose duty it is to 

 prepare the forecasts. In this country the hours for sending these 

 telegraphic reports are 7 a.m., 1 p.m., and 6 p.m., and at some sta- 

 tions also at 1 a.m. all times being Greenwich mean times. 



The observations usually sent are those of pressure, tempera- 

 ture, wind direction and force, humidity, visibility, sunshine, rain- 

 fall, cloudiness, general character of the weather, and certain 

 other more technical details. In order to obtain these data the 

 more important stations are equipped with a considerable instru- 

 mental installation, while at the smaller stations some of the 

 observations, such as those of wind force and direction, are made 

 by personal estimation, in which a very high degree of accuracy 

 can be attained by an intelligent and painstaking observer. 



Recording Instruments 



The instrument used for recording pressure is a barometer, 

 which in its standard form consists of a glass tube about 36 inches 

 long and 14 mc h or Vz mc ^ m diameter; the upper end of the 



