METEOROLOGICAL OBSERTATIOXS. 



207 



The Elastic Force of Aqueous Vapour is dependent upon the 

 temperature of the dew-point. Table VI. gives the elastic force 

 for every two-tenths of a degree of temperature, from lO"" to 89^, 

 the wliole degrees being given in the vertical columns headed -0, 

 and the tenths in the succeeding columns. 



The llelative Humidity can be calculated by dividing the clastic 

 force at the temperature of the dew-point by that at the tempera- 

 ture of the air {i.e. dry-bulb reading). Example : dry-bulb 55°-0, 

 dew-point 46°"5 ; the elastic force corresponding to these will be 

 "433 in. and •317 in. Therefore, dividing the latter by the former, 

 the result is 0'73; and taking saturation as 100, the relative 

 humidity will be 73. In Table VII. is given the relative humidity 



Table VII. — For the Determination of Relative Humidity . 



for every 5° of temperatiire from 30°-0 to 75°"0, and each degree 

 of difference between the dry- and wet-bulb readings from 1°'0 to 

 15°'0. This has been calculated to tenths to allow of the inter- 

 mediate values being obtained with precision. If whole numbers 

 are only required, the last figure should be increased when the 

 decimal is '5 and above. 



The foregoing are the necessary corrections, etc., to be applied 

 to the various readings before they can be utilized for comparison 

 with those at other places. In entering the observations in the 

 register it is absolutely essential that they be correcth/ copied from 

 the original note-book ; it is most desirable, therefore, that tlie 

 entries be afterwards checled by reference to the originals. In 

 filling in the barometer readings, the whole inches may be omitted 



