1869.] on the Scientific Exploration of the Deep Sea. 487 



The results are given in the quantity of Oxygen in fractions of a gramme 

 required to oxidize the Organic matter in a litre of water. 

 Average of 56 analyses of Surface-water : — 

 No. 



28. Decomposed °* 00025 1 Total 0-00095. 



28. Decomposable .... 0-00070 J 



Maximum. Minimum. 



Decomposed 0*00094 



Decomposable 0-00100 



Total 0-00194 



0-00000 

 0-00000 

 0-00000 



4 cases. 

 1 case. 

 1 case. 



a 



Total 0-00039. 



Average of 18 analyses of Intermediate water : — 

 No. 



9. Decomposed 0*00005 



9. Decomposable 0-00034 



In 7 out of 9 there was no "decomposed" Organic matter ; and in 3 

 out of 9 there was no Organic matter at all, as indicated by this test. 



In this series the analyses of the observations made during the Second 

 cruise are not included, as the calculations have been differently made. 

 Average of 60 analyses of Bottom-water : — 



No. 



26. Decomposed 0*00047 1 



34. Decomposable 0-00041 J 



Maximum. Minimum 



Total 0-00088. 



Decomposed 0-00105 0-00000 2 cases. 



Decomposable 0-00148 O'OOOOO 1 case. 



Total .... 0-00253 0-00000 1 case. 

 These figures appear to show (1) that Intermediate waters are more free 

 from Organic contamination than either Surface- or Bottom-waters, as 

 might be expected from the comparative absence of animal life in these 

 waters ; (2) that the total absence of Organic matter is least frequent in 

 Bottom-waters, and most frequent in Intermediate waters, Surface-waters 

 occupying a middle place in this respect ; and (3) that there is not much 

 difference between Bottom- and Surface-waters, either in the total quantity 

 of Organic contamination or in the relative proportions of the " decom- 

 posed " and "easily decomposable" organic matter. 



It may be worth notice that when the Bottom-water from great depths 

 was muddy, tests made before and after nitration showed that some of the 

 Organic matter was removed by this operation. 



