Electricity at the Kew Observatory. 



reasons already mentioned, this is not an important exception. There 

 is thus a certain amount of general support to Elster and Geitel's- 

 theory. An examination, however, of numerical details does not 

 seem favourable to any such intimate connexion between sunshine 

 and potential, as the formula suggested by them would imply. 



Taking, for instance, Table XIX, we notice in series III that, in 

 the afternoon, a mean potential of 106, answering to a mean of 3*6" 

 hours' sunshine, falls only to 101 when the hours of sunshine rise to 

 9'5. Again, in the forenoon observations of the same series, the mean 

 hours of previous sunshine increase fully six times, while the poten- 

 tial falls only from 111 to 93. 



The afternoon observations of series II are a striking illustration 

 of the diverse conclusions to which the different methods adopted in 

 Tables XVII and XIX may lead. 



Temperature. 



26. The forenoon observations of series IV, and both forenoon 

 and afternoon observations of series II associate high potential with 

 low temperature in both Tables XVII and XX ; and the balance of 

 evidence is unquestionably in this direction. The only sub-case in 

 which the two tables agree in associating higher potential with higher 

 temperature is the afternoon observations of series I, which, as 

 already explained, is the least important of the eight instances. 



On the whole, the evidence in favour of a connexion of high poten- 

 tial with low temperature is just about as strong as that in favour of 

 a connexion of high potential with little previous sunshine. 



Barometric Pressure. 



27. Higher potential is associated with higher pressure in the 

 forenoon observations of each of the four series both in Tables XVII 

 and XXI. In the afternoon observations, however, the higher- 

 potential is associated with the lower pressure in three cases out of 

 four in Table XVII, and in two cases out of four in Table XXI. The 

 phenomenon, in short, is an apparently clear association of high 

 potential and high barometric pressure in the forenoon, and an appa- 

 rent absence of any connexion in the afternoon. 



Wind Velocity. 



28. A somewhat striking similarity exists here to the phenomena 

 observed in the case of barometric pressure. 



In both the Tables XVII and XXII there is in the forenoon results 

 a conspicuous association of high potential with low wind velocity. 

 In Table XXII, it is true, series I observations form an exception, 



L 2 



