128 Journal of Meteorological Observations. 



The annexed Diagrams have been constructed from the 

 preceding Journal, as the simplest way of exhibiting at one 

 view, the differences in the pressure and temperature of the 

 atmosphere, as well as in the quantity of rain. The following 

 explanatory remarks will be useful. 



The upper Diagram is intended to shew the mean ascent 

 and depression of the mercurial column in the Barometer, 

 at the three different periods of observation in the day, 

 for each month in the year ; the three perpendicular faint 

 lines in each month's column indicating the three periods ; 

 the first being the morning, the second noon, and the third 

 night. The average mean of the whole is 30.067 inches. 



In the middle Diagram, the upper and lower lines shew 

 the extremes of temperature, or the highest and lowest state 

 of the thermometer in each month, the degree observed and 

 noted, being marked on the centre line of each month's 

 column. The upper middle line, shews the variations in the 

 mean temperature ; and the under middle line, that of the 

 dew-point; the observations being made at the same periods 

 of the day as those of the barometer. The average mean 

 temperature is 52° ; that of the dew-point 47°.7. 



From the results deduced by Mr. Howard, from twenty 

 years observations made by the Royal Society, it appears,, 

 as is stated in Mr. Daniell's Meteorological Essays, first 

 Edition, page 266, that the mean height of the Barometer 

 during that period was 29.8655 inches ; the mean tempera- 

 ture 49°.5 ; and the mean dew-point 44°.5. The mean 

 height of the Barometer in 1826 was 0.201 inch above that 

 mean, whilst the temperature and dew-point were also cor- 



