51 



mometer in vacuo. These values are oiven for the past five 

 yearSj and reduced to their means for eacli succeeding three 

 months of the year. 



The past year of 1883 lias been remarkable for its mani- 

 festation of solar energy. Again and again within that time 

 sun-spots have been visible to the naked eye, to say nothing 

 of the far greater number that the telescope has revealed. And 

 that this solar activity has been gradually increasing to a 

 maximum is evident from the mean values presented in the 

 foregoing table. But that table bears testimony also to the 

 increase cf the power of the solar evaporation of cloud, and 

 thence of invisible vapour, into the higher regions of the air, 

 and which must have been greatest during the past year. 



This will in some degree account for the heavy and con- 

 tinual fogs, and the excessive fall of rain during the last 

 three months of that year. For when the solar force is 

 minimised by the indirect action of the sun on the atmo- 

 sphere, which in our latitudes must take place in the latter 

 months of the year, the accumulated vapour, whether visible 

 or invisible, must fall to the earth and appear as fog or rain. 



The following table represents the rainfall in inches for 

 for the last three months of each of the years named, and 

 each is placed under the mean annual temperature of 

 solar radiation for the year, and beneath the amount of each 

 is placed the ratio which it bears to the rainfall of that year. 



