METEOEOLOGICAL JOURNAL. 75 
the Register. In order to shew you, as distinctly as pos- 
sible, the medium temperature and pressure of the atmo- 
sphere, here, at the hours of observation, I first took the 
two extremes of each monthly column of the Register, and 
adding these together, and dividing their sum by 2, obtained 
the medium, as you see it marked in the le/t hand columns 
of the tables for each year. In the next place, that I might 
ascertain more clearly the medium for each year, I summed 
up each monthly column with great care, and dividing the 
sum by the number of days in the month, obtained the 
medium as you find it marked in the right hand columns 
of the tables for each year. The rest of the tables will ex- 
plain themselves. 
I am, &c. 
W= Macritchie. 
