666 



PROCEEDINGS OF SECTION I. 



The table given below, kindly compiled by Mr. Cook from bis notes^ 

 shows the changes that have taken place in the thickness of the scum 

 at both the inlet and outlet ends of individual tanks during the 12: 

 months under consideration. In addition, the tanks that were in use 

 during the several months are indicated by an asterisk placed below 

 the figures for the month. The thickness was estimated by thrusting 

 a graduated pole into the scum to such a depth that on withdrawal 

 the liquid beneath was seen or heard rising through the resultant hole. 

 As a supplementary guide the disappearance of resistance to the passage 

 of the pole was of some service. For several reasons the measurements 

 given can only be considered as approximately representing the thick- 

 ness of the scum. In the first place, there is no very hard and sharp' 

 line of demarcation between the scum and the liquid contents of the 

 tanks. Although the upper layer of the scum is firm — but not dry,. 



Note.— At the end of June all eight tanks. 

 r=Small particle of flocculent matter — no continuous scum. 



