TRANSACTIONS OP THE SECTIONS. 



15 



its attendant planet, in relation to eacli other and to the sun, may balance and neu- 

 tralize each other. The barometer is thus placed in immediate connexion with the 

 winds proper to our climate ; and with the stin's place, by which these are mainly 

 governed. The artificial year, computed thus, is divided into four seasons, on the 

 principle of the daily mean temperature, and its balance between summer and winter, 

 spring and autumn, as shown in the before-mentioned work. The mean line for the 

 year is placed at 29'831 in., the average of the whole of the observations. Winter, as 

 here set out (from Dec. 7 to March 5), has a mean of 29-828 in. ; spring (March 6 

 to June 6), a mean of 29-833 in. ; summer (June 7 to Sept. 7), a mean of 29-879 in. ; 

 autumn (Sept. 8 to Dec. 6), a mean of 29"782 in. ; the whole progressive increase of 

 weight in the previous seasons being now lost by the prevalence of southerly winds, 

 and the decomposition of a portion of the aqueous atmosphere. 



The months are treated in the paper in succession : — 1, as to the barometrical 

 mean of the month ; 2, as to the range ; 3, as to the average rain ; 4, as to the 

 prevailing winds in connexion with these ; nearly the whole of the results cited 

 being to be found in the Tables. There are six of these ; two presenting the daily 

 observations of the direction of the wind during eighteen years, divided into classes 

 and assigned to the several months and years of the cycle, &c. ; and four com- 

 prising the daily mean of pressure, and notations of the wind for each day of the 

 artificial year in detail. 



This paper is accompanied (beside the Tables) with two diagrams ; one formed of 

 the monthly mean results of the pressure and rain, the mean range of the baro- 

 meter in each being added ; the other from the daily results above-mentioned. The 

 former presents a remarkable symmetiy in the mean pressure and mean rain, pro- 

 ceeding in opposite directions through their respective curves ; of the latter the 

 author considers that the elevations and depressions of the daily mean of the baro- 

 meter are here exhibited (on an enlarged scale), independently of the effect of lunar in- 

 fluence, in a curve which runs through the year by a regular movement of daily in- 

 crease or decrease upon the climatic mean ; the elevations, coloured red, being found 

 where we commonly experience our fair weather, and the depressions, coloured 

 gray, in those parts of the year most subject, in our latitudes, to rain and storms of 

 wind*. The equinoxes, it may be observed, are here both marked by the passing of 

 the curve below the mean ; the solstices, in winter by large depression, going off 

 gradually into the elevation connected with our fair-weather frost ; in summer by 

 continued elevation, though checked at this precise time by an approach to the mean 

 connected with tropical electrical disturbance and rain. The whole chart may be 

 perused in connexion with the Tables of the Winds (in which are found many beau- 

 tiful gradations indicative of system), to the improvement of our knowledge of this 

 important and hitherto little-explored branch of the subject. 



Table of Results to accompany the Monthly Diagram. 



These are distinguished in the Plate by the shadings. 



