408 



Scientific Proceedings, Royal Dublin Society. 



reached, values of 8"25-8'5 being obtained for them, and for clean large 

 ponds. Attention was also drawn by Saunders to the effect of photosynthesis 

 in raising the reaction of the water to as much as pH 9'0 in a small pond 

 containing masses of Spirogyra. 



The writer has examined a variety of natural waters, the reactions of 

 which are tabulated below. 



Table III. 



