TAKEK AT HOLLT BANK!, WATFOED, 1876-77. 



219 



cloud and force of the wiud observed at that hour ; and in some of 

 the other months there are several days on which no evening 

 observations were made, but the omissions are not so numerous as 

 to sensibly affect the monthly means. The mean temperature is 

 deduced from the observations of the dry-bulb thermometer at 

 9 a.m. and 9 p.m., and it will be seen to differ very slightly from 

 the mean of the maximum and minimum. The dew point ha\dng 

 been obtained from the readings of the dry- and wet-bulb by means 

 of ]\Ir. Marriott's ' Table for faciliating the Determination of the 

 Dew-point' (1874), Mr. Glaisher's ' Hygrometrical Tables' (6th 

 edition, 1876) were used in the calculation of the tension (or 

 elastic force) of vapour, and the relative humidity. 



Grouping into seasons some of the most important results here 

 expressed, we have the following table, which admits of ready 

 comparison with observations taken at other places. 



Watfoed. 



I will take for example the observations made at the Boyal 

 Observatory at Greenwich, as given in Mr. Glaisher's " Eemarks on 

 the "Weather," in the Quarterly Reports of the Registrar-General. 

 The values given for the mean pressure of the atmosphere are 

 corrected for elevation above the sea (160 feet), Mr. Glaisher's 

 monthly means not being reduced to sea-level. No other correction 

 has been applied. 



Geeenwich. 



