ea a a 

- other in value. 
ON ELECTRICAL OBSERVATIONS AT KEW. 147 
Tasie XLVIILI. 
Excess or defect of the mean electrical tension above 60 div. at each ob- 
_ servation-hour, as compared with the mean of each summer in the years 
1845, 1846 and 1847, and the mean of the three summers. 

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./Mean. 
—— | ———_—. 








div. | div. | diy. div. div. | diy. | div. (liy. | div. div. diy. 




-~|+)/+4+)/-|]-—) 4) - +) + 
TS45 000...) vooece 25°6 | 1071 | 13:7 | 17-8 | 38:4) 11°5 | 34:1 | 37-5 | 3:4 | 20°0 110°6 
— | + + | +/+ |4+|-|- 
-1846.]......| ...06.|40°8 | 27-9 | 9°0 | 10-0 {124:7|67°9 | 26-4 | 7:4 }246 | 6:7 (1133 
-}/-—|-| +)/-|+]-]-]-—] + 
RBA. ac tt) seves « 36:9 | 4:9 |18°0 | 38:1 | 41:0/53°5 | 28-2 | 25:4 1188 | 18:3 {107-7 









— | + +/t+}/+})-)-/-) + 
Mean.|......| ese | 33°9 | 7°99 | 7:4 | 152 1:5 | 42-7 | 13-9 | 24:9 {13-1 | 11°6 |110°5 
4 A.M. 10 ALM. 10 P.M, 2 A.M, 
In the annexed curves (fig. 11), 
the general irregularity which is 
apparent in the tables is very di- 
stinctly marked. We have already 
alluded to the maxima at 2 P.M. 
or noon; with one exception they 
are the highest of each curve; but 
how far, from the small number 
of observations that contribute to 
their determination, they can be 
regarded as truly representing a 
mean increase of the electrical 
tension above 60 div. at this pe- 
riod of the day, must, we appre- 
hend, be left for future observa- 
tions to determine. It is however 
likely that even on a long series of 
years the number of high tensions 
at noon and 2 p.m. will always 
bear a very small proportion to 
those at other hours, especially 
near the epochs of the forenoon. 
and evening maxima. In two of 
the aggregate summer curves, 
1845 and 1847, we have small 
subordinate maxima at 2 P.M., 
which, when compared with the 
two principal, are scarcely appa- 
rent. Nothing of the kind appears 
in the winter curves, either aggre- 
1845.—7F Mean. 
Fig. It. 
1846. = Mean, 
1847. 4 | Mean. 
with the mean curve of the three summers, 


<= 
oO 
> 
ce 
Mean diurnal curves of the electrical tension above 60 div. for the summers of 1845, 1846 and 1847, 
| gate or high tension, so that if the 
>. 4 A.M. 10 AM. 10 P.M. 2 A.M. maximum about 2 P.M. in summer 
truly represent a natural phenomenon, it is one peculiar to the summer 
+ 
months. The close approximation of the values of the means of each sum- 
_ mer is an interesting feature, which suggests considerable hesitation in de- 
_ ciding on the character of these irregular curves, The aggregate and low 
tension summer curyes also agree in their means, differing but little from each 
ra 
