74 DR. R. ANGUS SMITH ON THE EXAMINATION 



the air principally. The most dangerous bodies are pro- 

 bably in the water itself, and it is possible that they may 

 not be affected by the process of Column i . 



^^ I am not inclined to draw any important conclusion 

 from the total organic matter without inquiring into its cha- 

 racter. At present^ I believe, we are quite safe in attending 

 to the conclusions here given in Column i, with such pre- 

 cautions as I have elsewhere indicated — when, for example, 

 nitrites, sulphites, &c. are present. By and by we shall 

 learn the true mode of dealing with the other columns.^^ 



Having had occasion to examine another stream re- 

 ceiving sewage and flowing about twenty miles, the fol- 

 lowing results were obtained with the chameleon : — - 



Oxygen required by the decomposed and decomposing 



Matters. 



Grains per gallon. 



2-835 1-205 



1-249 1*630 



I '949 I "205 



1-170 1-453 



0-425 0*425 



0*815 0-177 



The gradual diminution of the decomposed organic 

 matter is here seen very plainly. As new sewage comes 

 in in certain places, the amount rises. 



These numbers correspond entirely with the apparent 

 condition of the stream. They do not, however, cor- 

 respond with the total volatile matter, which was as 

 follows : — 



ile matter. 



Fixed matter. 



9*33 



44-27 



623 



28-91 



399 



24-08 



3-08 



3675 



3*43 



31-85 



4-16 



30-31 



5*22 



29-92 



5'o4 



69-30 



I believe the results obtained by the chameleon arc 

 more useful in a sanitary point of view than the other 

 results. 



