1918] RXJKAL ENGINEEEINQ. 489 



the relative numbers were reversed aud there were 39 B. aerogenes to 1 

 B. colt. In sewage held in running water there was a rapid decrease of colon 

 bacteria which was more evident in the B. coli than in the B. aerogenes. At the 

 beginning there were about three times as many B. coli as B. aerogenes but 

 after seven days there were slightly more aerogenes than coli. 



A comparison of a collection of cultures from water with the characteristics 

 of similar collections from human feces and from grains showed a much greater 

 similarity bet«'een the water and fecal cultures than between the water and 

 grain cultures. This was especially true if those cultures evidently not of fecal 

 origin were eliminated from the water cultures and those of evident fecal 

 origin from the grain cultures. 



Samples were taken at intervals from streams known to be badly con- 

 taminated and the number of each colon type determined. In each case the 

 aerogenes type was greatly in excess above the source of pollution, but below 

 the sewer there were more B. coli than B. aerogenes. In one stream there 

 were no additional sources of contamination and the ratio of B. aerogenes 

 to B. coli found above the sewer was regained in about 10 miles. In the second 

 case there were other sources of contamination and the ratio of the two types 

 remained at nearly 1 : 1 for the eight miles observed. In this stream it was 

 found that while nearly all of the aerogenes cultures isolated above the sewer 

 were not adonite fermenters, below the sewer the adonite fermenters predomi- 

 nated. 



Observations on the types of organisms isolated from water after treat- 

 ment with calcium hypochlorite, M. A. Smeeton (Jour. Bad., 2 {1911), No. i, 

 pp. S55-359). — Experiments conducted at New York University with Croton 

 River water which had been treated with calcium hypochlorite in the propor- 

 tion of 1 part of chlorin to 2,000,000 parts of water showed that " the 

 organisms found were apparently of the common saprophytic type usually 

 found in air and water. No intestinal forms appeared to survive the treatment 

 in the amount examined. It would appear, therefore, that available chlorin 

 in the proportion of 1 part to 2,000,000 is sufficient to purify surface water 

 obtained under conditions similar to that of the Croton supply." 



The English incubation test for the putrescibility of sewage and sewage 

 effluents, F. W. Mohlman (Univ. III. Bui, H {1916), No. 5, pp. 315-324).— 

 This is an abstract of a thesis in which experimental work consisting of 

 incubation tests at 20° C. with various dilutions of sewage and distilled water 

 are reported, the purpose being to determine the value of the procedure rep- 



resented and modified by the so-called Phelps formula log q-= KG*. In this 



O = the final amount of oxygen present in the water in unit volume, C = the 

 concentration of the sewage in percentage by volume, t = the time in hours 

 allowed for the reaction to proceed, O' = initial amount of oxygen present, and 

 K = a constant determined by the character of the organic matter and in turn 

 defining the oxidizability of that organic matter. 



" Most of the results indicate that the oxygen consumption is nearly complete 

 in ten days. The variability in the amount of oxygen absorbed per liter of 

 sewage in different dilutions is excessive. The amount of oxygen absorbed depends 

 entirely upon the amount added and is always higher in higher dilutions. The 

 values of K seem to be more concordant, although they are generally higher 

 in higher dilutions. The excessive consumption of oxygen in higher dilutions 

 may be caused by the actual loss of oxygen gas, or may be caused by the 

 more vigorous oxidation. Whatever may be the cause, the fact remains that 

 the method did not give consistent results in varying dilutions. If the same 



