174 ; REPORT—1849, 
The double progression as a general rule is very apparent in the above 
tables. To the increase of tension from sunrise until 9 a.m. there are no 
exceptions ; two only to the diminution of tension between 9 a.m. and 3 P.M., 
and one only to the increase from 3 p.m. to sunset, The numbers are greatly 
in harmony at least in this respect with the results obtained from the discus- 
sion of the low tensions in the years 1845, 1846 and 1847, 
The exceptions to the double progression occurring as they do in the winter 
months, viz. January max. at sunset, February max. at 9 a.m., and December 
max. at sunset, are not without significance. In the discussion of the low 
tensions in the years 1845, 1846 and 1847, we adverted to the tendency ex- 
hibited by the winter curves to present a single progression; and while we 
noticed that the essential features of the double progression as exhibited in 
the aggregate curves were compressed as it were into the low tensions in the 
summer months, we also remarked that when the higher tensions—which 
were evidently more intimately connected with aqueous vapour, and were 
very much more numerous in the winter,—were withdrawn, the features of 
the double progression were withdrawn also, and suggested that upon a mode 
of directly observing the electrical tension of the aqueous vapour being 
devised, it might probably be practicable to separate it from the aggregate 
tension, and thus obtain a curve of a single progression representing the 
march of atmospheric electricity. The tables before us are strikingly confir- 
matory of the results obtained from the three years’ observations. We see 
here, as there, the double progression most decided in the summer months ; 
and the great. tendency to a single progression in the winter is quite as con- 
spicuous, if not more so than in those years. Upon the whole, the discussion 
of these seventeen months very strongly confirms the results already obtained. 
One point only remains for our consideration ; it is the annual period as ex- 
hibited by these numbers. It may probably be useful to particularize the 
annual period of each observation-epoch, and with this view the excess or 
defect as compared with the mean annual value of each epoch is given in the 
following table. 
TABLE XC. 
Excess or defect of the mean electrical tension (low, or below 60 div.) of 
each month in the year 1844, as compared with the mean annual value at 
each observation-epoch ; also the excess or defect of the monthly mean 
tensions, as compared with the mean of the year. 










Sunrise. 9 A.M. 3 P.M. Sunset. Mean. 
diy. div. div. div. div. 
v. 
January ....| + + 1:2 -| +183 | + 78 | 46S 
February ..| + 69 | +127 | +190 | + 66 | +12°0 
_ — 17 | 4+ 52 | + 15 | + 03 
April — 08 | +156 | — 63 | — 21 + 1:3 
May ......| — 81 | —15°7 | —186 | —151 | —141 
June ...... — 65 | —140 |} —12°5 | — 68 | —10°0 
uly: seyer &: 19 | — 04 | — 98 | — 31 | — 38 
+ 66 — 0s | — 68 — 13 — 06 
September ..} — 4°77 | — 12 | + 45 | + 49 | + 09 
October ....| + 18 | — 12 | — 23 | + 22 | + O1 7 
November ..| + 69 | + 86 | +103 | + 15 | + 68 
December ..| +11°9 | +13°5 | +253 | +18: 



