














ON ELECTRICAL OBSERVATIONS AT KEW. 135 
ence to which we particularly solicit attention is the augmentation in the 
summer curves of low tension of the forenoon and evening maxima, and their 
contraction in the aggregate summer curves. ‘This is very apparent on con- 
sulting the curves. In discussing the high tension during the summer months, 
this subject will be again referred to; in the mean time we may notice here, 
that upon the consideration of the high readings measuring the electrical ten- 
sion of aqueous vapour, it appears probable that these maxima depend on 
the presence of aqueous vapour for their development. 
TABLE XXVII. 
Range of the diurnal curves of electric tension below 60 div. in the summers 
of 1845, 1846 and 1847, and also in each year. 
Summer] Yearly 
Year. | curve. | curve. 



div. div. 
1845.| 15°9 141 
1846.} 15°9 | 15°0 
1847.| 20°7 | 18:3 
_—_——— | ———— | —_——__. — 
Mean.| 17:2 | 156 
TABLE XXVIII. 
Comparison of the excess or defect from the mean of the diurnal periods of 
summer, as deduced from the aggregate observations and from those below 
60 div. :; 
‘Value. |Mid.|2 a.m./4 a.m./6 a.m.|8 aml] 0 a.m.|Noon.|2 p.m.|4 p-m.|6 p.m./8 p.m.|10 p.m.| Means. 
_ 












div.| div. | div. | div. | div. div. div. | div. div. | div. | div. div. div. 
= OS ey Pesala —{—-/-/+]4] 4+ 
Aggregate ..-| 159] 19°4] 18°3 | 4°0 | 6:4 935 | 38 | 2-1 2:0 17 13°6| 26°2 | 37:2 
ee ae eae 
Below 60 div.| 5°8) 9°3} 9-3] 3-4 | 1:4 3:8 | 2°3 | 2:4 | 3:0 | 5:0 6°4 79 | 27-1 



The above table places the aggregate and low tension summer diurnal 
periods in contrast. 
Diurnal period below 60 div., Winter.—The following table exhibits the 
distribution of observations below 60 div. during the winter among the twelve 
daily readings. 
TaBLe XXIX. 
Number of positive readings below 60 div. at each observation-hour in the 
three winters of 1845, 1846 and 1847. 
Year. | Mid.!2 a.m.|4 a.m.|6 a.m.|8 a.m.|/10 a.m.|Noon. 2 p.m.|/4 p.m.|6 p.m.|8 p.m.|10 p.m.|Sums. 
—|—_——. 




1845. 87 | 101 | 99 | 12)101)| 76 76} 83 | 79| 69) 56] 65 | 904 
| 1846.) 94] 108 | 114} 12] 97] 75 75 | 66) 72) 50} 46) 62 | 871 
1847.) 74 | 107 | 126 6| 95] 84 80} 79| 78 | 66) 49] 64 | 908 
Sums.|255 316 | 339 | 30 | 293 | 235 | 231 | 228 | 229 | 185 | 151 | 191 |2683 





In this table, the greatest numoer of readings occur at 4 A.M., the epoch 
of the principal minimum, and the least number at 8 p.m., two hours after 
the evening maximum. It will be remarked, that the morning hours, viz. 2 
and 4A.m., exhibit the greatest number, and the evening hours; 6, 8 and 
10 p.m., the least. The thirty readings at 6 A.M. are excepted, for the reason 
stated on page 130. 
