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VT. A Discussion of Atmospheric Electric Potential Results at Kew from 
Selected Days during the Seven Years 1898 to 1904. 
By C. Chree, Sc.D., LL.D ., F.R.S. 
{From the National Physical Laboratory.) 
Received February 21, —Read March 15, 1906. 
Contents. 
Sections Page 
I- 3. Nature of observational data.299 
4. Mean monthly and annual values of the potential gradient.301 
5. Non-cyclic effect.303 
6-7. Diurnal inequality.305 
8. Analysis of diurnal inequality in Fourier series.309 
9. Annual variation (Fourier series).311 
10. Comparison with previous results for Kew.312 
II- 15. Comparison with Chauveau’s results for other stations.313 
16. Irregular diurnal changes.319 
17. Special meteorological features of the selected days.320 
18-25. Connection of atmospheric potential with meteorological elements.322 
26-32. Appendix.—On the relation between the regular diurnal changes of barometric pressure 
and potential gradient.329 
§ 1. In 1894 special observations were commenced with the object of determining the 
influence of its position on the records from the Kew water-dropping electrograph, 
and also of ascertaining whether any alterations were desirable. The results were 
discussed in a paper* communicated to the Society in 1896. 
The experiments led to certain changes in the apparatus, and an auxiliary system 
of eye observations was introduced with the object of obtaining quantitative results 
possessing a definite significance. 
The original water tank was replaced by another of much larger diameter and small 
depth. The new tank is situated on the wooden roof of a detached portion of the 
north-west room on the ground floor, which contains the recording part of the 
electrograph. The wire connecting the water-dropping tube to the electrograph is 
* ‘Roy. Soc. Proc.,’ vol. 60, 1896, pp. 96-132. 
VOL. OCVI.—A 407. 2 Q 2 30.6.06 
