176 REPORT—1849. 
turbing influences of clouds. The curve of cloudiness, as deduced from six 
years’ observations at Greenwich, will be found on page 198. The approxi- 
mation towards agreement in the sunrise and sunset curve is greatly in ac- 
cordance with the phenomena already noticed in the same curves from five 
years’ observations (see page 162); and the differences.observable between 
those for the year 1844 strongly confirm the remark that has been offered, 
viz. that a series of five years’ observations at least is necessary to eliminate 
the effects of irregular movements. It may be remarked, in immediate con- 
nexion with the curves of 1844, that the sunrise curve is much more in ac- 
cordance with the sunset than that at 9 a.m. is with that at 3 p.m. 
TABLE XCI. 
Annual range of the electrical tension at the four observation-epochs in the 
year 1844. 




- Epoch. Range. 
v: div. 
Sunrise....| 20°0 
Samy. oss | ols 
Spm.....| 43°9 
Sunset .... 33°4 


Mean .... 30°5 
Part I]—NEGATIVE ELECTRICITY. 
The exhibition of negative electricity being confined within very narrow 
limits as compared with that of positive—the number of readings being ex- 
tremely few—renders it exceedingly doubtful whether we can at all hope to 
find anything like a diurnal period manifested by it. The number of read- 
ings in the three years 1845 to 1847 amounted to 324, and it is not difficult 
to obtain the mean reading at each observation-hour from these records. — 
In the seventeen months prior to 1845, great care was manifested in ob- 
serving every and even the minutest change in the kind of electricity with 
which the conductor was charged. Not a shower appears to have occurred 
but it was minutely watched, the rapidity and extent of the changes assidu- 
ously observed, and the length of the sparks carefully measured ; the whole 
being accompanied by notices of the weather at the time which appear to 
possess great accuracy of detail. As however the extremes of the charges 
are usually set down in some cases at the times they occurred, in others ina 
more general manner and between certain epochs, and not at such regular in- 
tervals, except on certain occasions, as would be useful in discussing them with _ 
a view to determine a diurnal period; such discussion, with regard to the nega- 
tive observations previous to 1845, has not been attempted ; but they have 
been carefully arranged in Table XCII. under the heads of “ Limits of Time,” 
“ Extremes of Charge,” “ Maximum Length of Spark,” and accompanying 
“ Weather and Remarks.” Under the last head are included the state of the 
weather with remarks by the observer at Kew; the clouds or other phzno- 
mena (likely to illustrate the Kew observations) recorded at or near the 
same epochs at the Royal Observatory, Greenwich, and occasional remarks 
by the writer. All remarks having reference to the Greenwich Observatory 
are placed within brackets. 

