286 Mr. E. EL Nichols on the Diurnal 



The results for July give a more detailed account of the 

 electrical conditions, as the negative charge was also mea- 

 sured and observations commenced three hours earlier. The 

 range for the conductivity is considerably less than for the 

 other months, there being a maximum at 1 p.m. and a 

 minimum during the night. There is a curious well-marked 

 minimum at 11 a.m. which corresponds to a maximum 

 electric charge. Individual results show a minimum at 

 11 a.m. for July 23, 2S, and 30, while for July 21 there 

 is one at 9 A.M. The minimum at 11 h. appears in the 

 3-monthly means, and the depression from 10 a.m. to 1 P.M. 

 is more pronounced still in the Eskdalemuir results discussed 

 below, so that it is probably a real phenomenon. 



Although the data for the individual days cannot be dis- 

 cussed in detail, a few points may be noticed. There 

 appears to be no definite effect of precipitation on the elec- 

 trical quantities as a general rule, but there are cases in 

 which a considerable decrease in electric charge or con- 

 ductivity has been observed to follow rain (see Table III.). 

 In the few measurements made before and after thunder- 

 storms, the electrical values obtained show nothing abnormal. 

 Usually there is a similarity between the variation of the 

 conductivity and the positive and negative charges, the two 

 latter showing a close agreement. There is also a definite 

 minimum about midday in the ratio of the positive and 



^ ), which is obviously associated with 



LJL1C BiJlitl cjli_cul. ~' 



A partially successful attempt was made on June 29-30,. 

 1914, to obtain the electrical variation for the complete 

 24 hours, observations being commenced at 7 a.m. on 

 June 29 and continued hourly till 7 a.m. June 30 (see 

 Table II.). After 9 P.M., however, the Wilson electroscope 

 failed owing to insulation trouble, which is a great diffi- 

 culty in night work. For such work an electric torch must 

 be used for reading, oil lamps being fatal to results, because 

 of the production of conducting gases. The diurnal varia- 

 tion of electric charge gave some indication of a double 

 period with primary maximum and minimum about 4 p.m. 

 and 4 a.m. respectively. The values for both charges were 

 lower at night than during the day. The ratio of the charges 



I .=± \ shows a remarkable maximum at 3 a.m.. and a mini- 

 mum at 12 noon. Such an outstanding maximum might 

 appear fortuitous, but similar examples of high maxima 

 occurred on July 23 at 4 a.m., July 28 at 5 A.M., and 

 August 4 at 5 a.m. 



