84 Proceedings of the Royal Irish Academy. 



Absolute Volume Comjiosition in Cuh. Cents. 



Carbonic acid, 32-588 



Oxygen, 9-949 



]S'"itrogeu, . , 13-812 



Total, . . . 56-349 



1,000,000 litres of water contain 23,285 litres of mixed gases. 



It will be desirable to compare the relative quantities of oxygen 

 and nitrogen obtained in these analyses with the relative proportion of 

 these gases which would be dissolved by a pure water, in contact 

 with ail". Bunsen has determined, that in 100 parts of oxygen and 

 nitrogen, dissolved by pure water, the relative proportions are — 



Oxygen, 34-91 



Mtrogcn, 65-09 



Comparing the results of our analyses of the Yartry waters with 

 this determination, we find that in 100 parts of dissolved oxygen and 

 nitrogen the following relative proportions obtain : — 



Xc. I. 



Oxygen, 32-39 



!Xitrogen, : . . 67-61 



No. II. 



Oxygen, 32-34 



Nitrogen, 67-60 



From this we see that these relative proportions of oxygen and 

 nitrogen pretty closely agree with those which are found in a pure 

 water; but there has been a slight diminution in the proportion of 

 oxygen. 



Now, if a diminution of oxygen is brought about, in consequence 

 of oxidation of decaying organic matter with which a water comes in 

 contact, then, in the Yartry water, such contamination would seem to 

 have occurred only to a very small extent; and, therefore, on this 

 supposition, it is free from injurious organic constituents. 



Making the same comparisons for the Canal waters, we obtain the 

 following : — 



No. I. — From Haroldscross Bridge. 



Oxygen, 26-16 



Nitrogen, 73-84 



No. II. — -From Leeson-street Bridge. 



Oxygen 33-368 



Nitrogen, 66-632 



