PREFACE. 



IN the preliminary Chapter on the Atmosphere 

 I have referred to De Luc's * Recherches sur 

 1' Atmosphere,' Robertson on the Atmosphere, 

 and Dalton's Essays. The barometric table of 

 the mean height of the mercurial column for 

 every day in the year is, I believe, the first of 

 the kind that has been deduced ; it is the result 

 of thirty years' observations, made by myself in 

 one locality. In the name of " Henry" my table 

 of daily mean temperatures was used for two 

 or three years, at the Royal Observatory, as a 

 standard of comparison for the temperatures 

 in the weekly report of the Registrar-General, 

 and it was only discontinued when the esta- 

 blishment had accumulated sufficient data from 

 which to deduce a standard of their own : that 



