an Ulster and Geitel Electrical Dissipation Apparatus. 485 

 Table VII. — 3G months taken individually. 





Number of months when largest 

 value of 



a + . 



a-. 



$• 



?'• 



P. 





9 

 24 

 10 

 25 



10 



26 



9 



28 



20 

 19 

 20| 

 15 



20 

 21 

 20 



1SJ 



28 

 11 



B ,, ,, temperature. 



„ „ ,, pressure 



of most cloud 





when the other is small. For instance, in 9 months the 

 mean value of a + was larger in the group of days of highest 

 potential, leaving 27 months in which the larger mean value 

 of a + belonged to the group of days of lowest potential. 

 The tendency is thus for high values of a + to be associated 

 with low values of P, and conversely. A case in which the 

 means from the two groups of days were exactly equal was 

 counted as J. 



If, instead of taking the three years separately we take 

 them combined, we get the following results instead of those 

 in Table VII. The number of months being now 12, the 

 criterion lor association is a decided departure from the 

 figure 6. 



Table VIII. — 3 years combined. 





Number of months when largest 

 value of 



a+. 



a~. 



Q- 



P. 



in group of days of highest P 





 8* 



3 

 9 



1 

 10 



3 

 11 



7i 



9 



7* 



5 



3 

 11 



2 



,, , ,, temperature. 



,, ,, ,, pressure 



,, ,, of most cloud 



§ 9. The somewhat curious fact that the difference between 

 the two mean values of P in Table III. was in each season 

 exactly the same fraction of the mean seasonal value, makes 

 the comparison especially instructive. 



It is clear from Table VIII. that there is a distinct 



