
ON ELECTRICAL OBSERVATIONS AT KEW. 151 
: ( bas Taste LIII. 
Number of positive readings in each month of the three years 1845, 1846 
v and 1847. 


‘1845. 287 | 258 | 228 | 280 | 305| 299 | 330 |313| 318 | 287/220|249| 3374 
1846.| 264 | 228/276 259 | 308} 308 | 327 |314| 316 | 269 | 280| 250! 3399 
1847. 244| 226 |278| 271 | 313| 300 | 320 |/315| 318 |298/265|255| 3403 
—_—|§ —— |} —— | |) | | LT | 


Sums. 795 | 712} 782) 810 | 926 | 907 | 977 | 942) 952 | 854 | 765 | 754 | 10176 

TABLE LIV. 
Mean electrical tension of each month in the three years 184.5, 1846 and 
1847, with the mean annual period, as deduced from the whole. 
Year.) Jan. | Feb. | Mar. April.|May._ June.| July. | Aug.| Sept. Oct.| Nov. Dec. ‘Mean. 
div. aly. div. | div. div. | div. | div. | div. | div. | div. | div. | div. | div. 
1845.| 1093) 190-3) 64-5) 56-1 | 38-7) 26:0 | 25:9 | 29-9) 37-5 | 46-2) 83-9] 84-2] 63-1 
1846.| 95-9} 100°1| 78-9) 63-7 | 42°8) 33-0} 31°3 | 26-3) 27-2 | 656) 49-8/160-3 | 61°3 
1847.| 258-8) 2066] 79-6) 52-2 ia] 28°8 | 59°7| 31:9) 34°3 cat | 78°7| 84:°3| 76°3 
Mean.| 150°7| 166°6| 75°0| 57:2 37°9) 29°3 | 38°8 | 29°4| 33:0 















50°5) 69°6)109-5| 66:9 

TABLE LV. 
Excess or defect of the mean electrical tension of each month, as compared 
with the mean of the year for the three years 1845, 1846 and 1847, and 
the mean annual period. 

Year.| Jan. | Feb. Mar.| April. May. June, July. | Aug.| Sept. Oct. Nov. Dec. |Mean. 
| | —_—| 
diy. | div. | div. | div. | div. | div. | div. | div. | div. | div. | div. | div. | diy. 
+} 4) 4 ~j}—]—/}—| — |} 4] 4 
1845.) 46:2 |127:2| 1-4) 7:0 | 24:4) 37:1) 37-2! 33:2} 25°6| 16-920°8| 21:1) 63°1 










+] 4+) 4 —} =} -/-|-|+/—| 4 
1846.) 34-6] 38°8 17°6| 2°4 | 18°35) 28°3| 30-0| 35-0) 34:1) 4:311°5| 99:0} 61:3 
+ | + 
ska te 130°3 
| a | 
+ =| —/}/—]/—-|—|—/+) 4 
3°3 | 24°1 | 44:0) 47-5 | 16°6 | 44-4 42°0 | 35°3 2:4) 8:0] 76°3 


—_ | —— | | 



+ | =— 
Mean. 2°7| 42:°6| 66°9 




+/+ }/+)-/-|- | -/--| - |- 
83°8| 99°7| 8-1] 9°7 | 29:0) 37°6| 28:1 | 37°5| 33-9 | 16-4 

An annual period in the electrical tension is not only very perceptible, but 
unquestionable. It is, with an exception hereafter to be noticed, a single 
progression having its turning-poiuts in February and June. The exception 
alluded to consists in an increase of tension in July ; but as this occurred only 
in one year (1847), it will form the subject of remark further on. From the 
mean of the three years, we find that June and August present nearly the 
same electrical tension, the difference being only 0°1 div. In September a 
small rise occurs which is increased in October; the augmentation becomes 
more rapid from November to January and then receives a check, the Fe- 
bruary increment being less than those of December and January. In 
February the maximum is attained, which is succeeded in March by a very 
rapid diminution of tension which continues through April and May, the 
decrements becoming less in value until June, the month presenting the 
lowest tension. 
From this progression those of individual years differ to a greater or less 
