668 



PROCEEDINGS OF SECTION I. 



It will be seen that tlie tanks were used in combination as follows 

 Table II. 



Tank— 



1905. 

 November 

 December 



1906. 

 January . . 

 February . 

 March . . . 

 April .... 



May 



June 



July 



August . . . 

 September 

 October . . 



No. 4. 



1 = Tank in operation. 



= Tank idle. 



Tank No. 1 — wbicli was idle from November until Marcb — 

 presented 6ft. of scum at the inlet in the first-named month, and a few 

 inches at the outlet, which means that the tank space was almost 

 occluded at the inlet. This amount gradually lessened, until in March 

 it stood at about 3ft. After being used for five months in combina- 

 tion with three or four other tanks, the scum was but a few inches thick 

 distributed in practically the same ratio. For the last four months 

 it was worked with only two other tanks (Nos. 2 and 3), and while the 

 scum at the inlet remained about the same that at the outlet more than 

 doubled. 



Tanks Nos. 2 and 3 were thrown out in December, when there 

 was 7ft. 6in. of scum at the inlet — practically solidified to the bottom — 

 and remained so until April, when about half the solids had liquefied. 

 For the next three months they were worked in combination with two 

 other tanks, and at the end of the time they showed a diminished 

 thickness. Since then they were used with No. 1, as already mentioned, 

 and present an increase most marked, as in the case with No. 1, at the 

 outlet. 



These three tanks have this in common, that at their respective 

 inlets the scum at one time accumulated to a much greater extent than 

 in any of the others. This is probably due to their situation with regard 

 to the main carrier. Being the first tanks to which the sewage has 

 access, it appears reasonable to assume that they receive a larger 

 proportion of the suspended matter than the others. 



After working for the first eight months and resting for the re- 

 maining four, No. 4 tank contained about the same thickness of scum 

 as it did at first. 



Tanks Nos. 5 and 6 were idle for seven months, and Nos. 7 and 8 

 for nine months respectively. There is a marked tendency towards 



