128 Dr. C. Chree. Observations on Atmospheric 



Vapour Density. 



23. In Tables XVII and XVIII the forenoon observations of 

 series IV, and both forenoon and afternoon observations of series II, 

 support Exner's theory to a certain extent, inasmuch as they decidedly, 

 on the whole, associate higher potential with lower vapour density. 

 The forenoon observations, however, of series I lead in both tables 

 to exactly the opposite result. Also in Table XVII, in five cases 

 oat of eight, the higher potential is associated with the higher vapour 

 density. In some instances, e.g., the afternoon observations of 

 series III and IV, Tables XVII and XVIII lead to diametrically 

 opposite conclusions. The following are instances of corresponding 

 means of vapour density and potential, culled from the several tables. 

 In Table XVIII, 8'12 occurs with both 185 and 93 ; in Table XT, 

 6-64 with 229 ; in Table XII, 6'62 with 180 ; in Table XVII, 6'57 

 with 204, 6'35 with 342, and 6'31 with 237 ; in Table XVIII, 6'6l 

 with 141, 6-45 with 168, and 6'39 with 170. Again, in Tables XV 

 and XVI we find 6'10 associated with 273, and 6'17 with 217. Lastly, 

 in Table XVIII we have the following combinations, 5'46 with 219, 

 5-40 with 333, 5'37 with 171, and 5'27 with 147. 



In the face of such results, ifc seems difficult to believe in any 

 intimate and uniform connexion whatsoever between potential gradient 

 and vapour density. 



Relative Humidity. 



24. No special table is devoted to this. In Table XVII no less 

 than six sub-cases out of eight associate higher relative humidity 

 with higher potential. It will be noticed, however, that in three out 

 of the six sub-cases referred to the differences between the mean 

 humidities answering to the two groups are smaller than in either of 

 the two sub -cases which associate higher relative humidity with 

 lower potential. With the exception of the forenoon observations of 

 series I, and the afternoon observations of series III, the differences 

 between the mean relative humidities in the two groups are very 

 small. Thus, on the whole, the evidence in favour of any distinct 

 association of higher relative humidity and higher potential is insuffi- 

 cient. 



Sunshine. 



25. There is in both the Tables XVII and XIX a balance of 

 evidence in favour of a connexion of low potential with long previous 

 sunshine. Out of eight sub-cases in each table, five favour this con- 

 nexion in Table XVII, and six in Table XIX. The only sub- case in 

 which the tables agree in associating higher potential with longer- 

 previous sunshine is the afternoon observations of series I, and, for 



