156 REPORT—1849. 
and it is only after we have examined the yearly and summer curves that 
we find a tendency to a single progression in the winter. In the annual 
curve it is the aqueous vapour that produces the single progression ; this is 
very apparent in the aggregate curves. When however we remove the ten- 
sions that appear more immediately to result from the presence of aqueous 
vapour, this single progression is interrupted at those points at which it is 
probable the influence of the vapour may be less than that of atmospheric 
electricity, and at these points only we have a corresponding elevation and 
depression. From the above considerations, both with regard to the diurnal 
and annual periods, we apprehend that it must be concluded, that a mere 
arbitrary division of the readings at any particular point will fail effectually 
to separate the electrical tension into its constituents, viz. that which is de- 
pendent on the solar action from that which results from the presence of 
aqueous vapour: nevertheless it appears, we apprehend, highly probable that 
the indications of a diurnal as well as an annual progression of atmospheric 
electricity, each having an ascending and descending branch, and consequently 
both being single progressions, are by no means of an uncertain character, 
and that the only requisite is a suitable mode of observation in order to apply 
formule capable of effecting such a separation, whereby all electrical tensions 
resulting directly from the presence of aqueous vapour may be ascertained and 
deducted from aggregate tensions as measured by the electrometers ; that the 
curves both of atmospheric electricity and the electrical tension of aqueous 
vapour may be exhibited each freed from the influence of the other, so that 
their connexion or non-connexion with other meteorological elements may 
be readily ascertained. 
High tension—In the following table the great difference between the 
high readings in summer and winter is very apparent : February furnishes 
the greatest number (413) and June the least (59) ; the proportion is exactly 
7 tol. 
TasLe LXII. 
Number of positive readings above 60 div. in each month of the three 
years 1845, 1846 and 1847. 
ee a ee 
Year.| Jan.| Feb.| Mar.| April.|May.| June.} July. |Aug.| Sept. | Oct.|Nov.| Dec.|Sums. 



1845.|103|/151}) 83] 69 | 48) 22 | 15 | 26 7 | 81|107| 100} 852 
1846.|118|119|124} 87 | 40] 28 | 21 | 17] 25) 71} 87)177| 914 
1847.,165|143}111| 81 | 24) 9 | 47 | 23| 39] 45] 91/103) 881 
Sums.| 386 | 413 |318| 237 |112] 59 | 83 | 66 | 111 | 197 | 285] 380 | 2647 

Tasie LXIII. 
Mean electrical tension above 60 div. of each month in the three years 1845, 
1846 and 1847, with the mean annual period, as deduced from all the 
positive readings above 60 div. 


Year.| Jan. | Feb. | Mar. |April.| May. | June.| July.|Aug.| Sept.| Oct. | Nov. | Dec. |Mean. 
1845.) 258°5| 303-5) 127-1) 138*8) 110°8) 82-1] 98-3) 94-4) 95:3 98-5 138°3 167°1| 173-2 
1846.| 171°5| 160-0} 132°7| 127°7| 145°3| 94°6| 71:3) 97:6) 78°4|155°7| 92-0) 211-0) 149-7 
1847.) 364°2) 305°5| 146°3| 91:6) 91-2) 68°3 | 194°8) 72°5| 76:2 | 124-4| 168°2) 156°9) 205°6 
Mean.) 277°1| 262-8} 136-0] 118-6) 118°9} 85:9 | 146-1) 87°6| 84:8 | 125-0) 133-7) 184-8) 175-9 

