1920] RURAL ENGINEERING. 791 



flock in Missouri i.s from 100 to 150 hens, this lionse is 20 ft. square, a square 

 houso beinjx tlie most economical to construct and affording a maximum amount 

 of floor space. 



Economics of a sound house, H. B. Young {Cornell Readiny Course for the 

 Home, No. 131 {1919), pp. 8, figs. 3). — Brief popular information on the plan- 

 ning of a farm house is given. 



The preliminary treatment of sewage, J. H. Edmondson {Surveyor and 

 Mimic, and County Knyin., 58 {1920), No. lJf87, pp. Itl-U).—\ number of 

 laboratory ana practical experiments on the preliminary treatment of sewage, 

 including particularly the use of chemicals for clarification, are reported. 



It is concluded that while laboratory experiments give useful information 

 as to the value of various chemicals <m a particular sewage, they do not neces- 

 sarily represent working-scale results. In considering chemical precipitation 

 tlie design of the settling tanks is considered to be quite as important a factor 

 as the nature and class of the sewage to be treated. Sludge disturbance was 

 found to be inhibitory to efhcient .settlement, particularly when iron salts were 

 used as the precipitant. Even small quantities of iron added with aluminum 

 sulphate had an adverse effect upon settlement in conjunction with sludge dis- 

 turbance. The formation of iron sulphid in settling tanks is concluded to cause 

 many difliculties in the eflicient purification and disposal of sewage. 



Action of the microbes of sewage purified by the activated sludge process 

 on albuminoids, urea, and nitrates, P. Courmont and A. Rochaix {Compt. 

 Rend. Acad. Sci. [Paris'], 110 {1920), No. 16, pp. 967-970).— Studies of the 

 action of organisms isolated from sewage purified by the activated sludge process 

 on albuminous matter, urea, and nitrates are reported. Only seven species of 

 organisms were isolated from the eflluent used. 



It was fo.und that with two exceptions these organisms showed indol produc- 

 tion, but with the exception of Bacillus subtilis had no action on coagulated 

 serum, gelatin, egg albumin, or milk casein, althougli showing an energetic 

 proteolytic ferment. Three of the organisms fermented urea, B. subtilis had a 

 slight action, and the other three organisms were without action. Five of the 

 seven organisms were found to have a direct denitrifying action on solutions 

 containing potassium nitrate. 



A correlation study of the colon-aerogenes group of bacteria, with 

 sjiecial reference to the organisms occurring in the soil, C. C. Chen and 

 L. F. liETTGKK {Jour. Bttct., 5 {1920), No. 3, pp. 25S-298, figs. S).— Experiments 

 conducted at Yale University are reported (1) to determine the relative fre- 

 (luency of the colon and serogenes types of bacteria in soils which from all 

 appearances are free from animal pollution, (2) to ascertain whether or not 

 there is a definite correlation between types of bacteria and their origin, and 

 (3) to' study the coli and serogenes types of gas-fermenting organisms with 

 reference to some of the most important reactions and media. Soils of known 

 .sanitary quality were used. 



The studies showed the great predominance of the serogenes-cloacaj type. 

 Of 467 strains of bacteria isolated from various soils, 430 were identified as 

 Bacterium (crogenes, 17 as B. cloaca; and only 20 as B. coli. Furthermore, the 

 sources of the coli strains were shown by the sanitary survey to be not entirely 

 free from animal pollution. All of the 173 organisms found in the feces of 

 .7 men, 2 monkeys, and 14 domestic animals were typical B. coli. It is apparent 

 from these observations that there is a definite correlation between these types 

 of bacteria and their origin. An almost perfect correlation could be established 

 by the methyl red, the Voges and Proskauer, and the uric-acid tests. 



The limiting hj'drogen-ion concentration of the coli cultures, as determined 

 by the colorimetric method, varied from pH 4.5 to 5.6 in the synthetic medium 



I 



