158 REPORT—1849. 
Tabet LXIV. 
Excess or defect of the mean electrical tension above 60 div. 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. 













div. | div. | div, | div. diy. div. | div. | div. | div. | div. | div. | div.] div. 
+{4+/—-|}-|-—-]|-]/-|-/-]-/-|- 
1845.| 85:3} 130:3| 46-1) 34-4} 62:4) 91-1) 74-9] 78-8) 77-9) 74-7| 34-9] 6-1] 173-2 
+|/+\/-|-|-|-|)-|-]-j4+]-]4 
1846.) 21-8} 10°3)17:0| 22:0) 4:4) 55:1) 78°4| 52-1) 71:3) 6-0) 57°7| 61°3| 149-7 
+/+ {/—-)-—-}-]}]-|-/]-]-|-|-]- 
1847.| 158-6} 99-9] 59°3| 1140) 114-4) 137-3) 10°8 | 133-1) 129°4| 81-2) 37°4| 48°7| 205°6 
—_ | | | | | | | | | | | 


+/+ )—-}-}/-/-|-|- | -}-]-]4+ 
Mean.| 101:2} 86°9/39°9) 57:3) 57:0} 90-0) 29°8} 88-3) 91-1) 50-9) 42-2) 8-9) 175-9 



Srction 2.—Discussion of Observations at Sunrise and Sunset. 
The observations made at sunrise and sunset furnish two series from which 
an interesting comparison with the mean annual period as deduced from 
three years’ observations (see p. 151) may be derived. The epochs of obser- 
yation of course are variable, coinciding in the summer with those points of 
the diurnal curve that are situated nearer the two superior turning-points, 
the principal extremes ; while as regards the epochs of winter, that of sunrise 
approaches within two hours of the forenoon maximum, and that of sunset 
nearly coincides with the afternoon minimum. That this variability influ- 
ences, no doubt to a considerable extent, the exhibition of electrical tension 
at the epochs of sunrise and sunset, there can be no question. Upon consulting 
Table V. (p. 118) it will be seen that the sunrise observations throughout the 
year, with the exception of those just about midwinter, fall in that portion of 
the diurnal curve that is below the mean of the whole year; while those at 
sunset appertain to a portion of the curve above the mean. We are there- 
fore prepared to expect that the sunset observations throughout the year 
should present higher electrical tensions than those at sunrise, and such is the 
general fact—the tension at sunset is with but few exceptions higher than 
that at sunrise. 
The entire number of observations employed in the deduction of the fol- 
lowing results is 3367 ; of these, 1712 were made at sunrise and 1655 at sunset. 
The following tables exhibit the distribution of these observations over the 
respective months of the five years during which they were made, and also 
the mean of each month as based upon these numbers. 
TABLE LXV. 
Number of positive readings of the electric tension at sunrise in each month 
from August 1843 to July 1848 inclusive. 

Year.| Jan.| Feb.|Mar.| April.|May.| June.|July.|Aug.| Sept.| Oct.|Nov.|Dec./Sums. 
TBAS ce] Pavel!) eon ee aoe es coe | P26.) 030 | 24 SOT a 
1844.| 28} 28] 27} 30] 31] 30] 30] 28| 24-| 28) 28] 31] 343 
1845.) 26} 27| 23) 29] 31] 24] 27] 28] 30] 30) 30) 31) 336 
1846.) 30] 27); 30} 26] 31} 26 | 27] 30] 29} 27) 30} 30) 343 
1847.) 31| 27) 31] 28 | 30] 24] 29} 29] 30] 31] 29/728] 347 
18483) 6305) 629) 2B SOs eSL| 2B 6284) sees Wy see bet call ieecuen| ieeel Meee 


—_|-. —_—~ — | | _ 

| 
Sums.| 146 | 138 |139| 143 | 154} 132 |141| 141] 143 | 140) 144] 151] 1712 








