I 100 to 11.36 100 to 11.30 



150 PROCEEDINGS OF SECTION B. 



Lake Forsyth. Sumner. 



Chlorine ... 19276.5 per million 18815.0 per million. 

 Sulphuric anhydride 2191.5 „ 2126.6 



Ratio of chlorine to 

 sulphuric anhydride 



If we assume that the whole of the chlorine in rain is derived 

 from sea spray and compare these figures with those representing 

 the ratio of chlorine to sulphuric anhydride in the different 

 seasons, we find that one half at least of the sulphuric anhydride 

 is obtained from other sources than sea water. 



Ratio of chlorine to sulphuric anhydride in rain-water at 

 different seasons. 



CI. SO3 



Spring 100 ... 22.5 



Summer ... ... ... 100 ... 25.3 



Autumn 100 ... 27.8 



Winter 100 ... 23.0 



Mean of whole year ... 100 ... 24.9 



The increased amount is probably due to volatile compounds of 

 sulphur disengaged in the decomposition of organic substances, 

 which proceeds more rapidly during the warmer months. 



The influence of winds from different quarters probably affect 

 the results, but in what way it is difficult to ascertain. Our 

 results have been compared with the prevailing direction of the 

 wind, but as yet without shewing any decided influence. The 

 characteristic hot "nor-westers" experienced here, probably aftect 

 the results most, but rain is seldom received in any quantity from 

 this quarter, and several attempts to secure samples have proved 

 fruitless. Indications might be given in the rain-water falling in 

 the "sou'-westers" which frequently follow the former wind, such 

 however as yet have not been examined. 



The results in Table YI, shew the true average composition of 

 rain-water in the several seasons in parts per million. The 

 numbers are obtained by dividing the numbers of pounds of rain 

 per acre into the weight of each constituent, and multiplying the 

 result by 1,000,000. The richness of the rain in solids during 

 spring, summer, and autunni seems to be fairly constant, but 

 there is a considerable fall in the winter season. The albuminoid 

 nitrogen is greatest in summer, due pi'obably to the increased 

 vigour of all forms of life during this pei'iod. The nitrogen as 

 ammonium compounds appears to be about equal in spring and 

 summer, while the nitrogen present as nitric acid is more 

 abundant in the spring. It is curious to note that the total 

 nitrogen decreases in the successive seasons. 



