At the Royal Testing Station in Berlin, numerous experiments on sewage chlorination were made by Kranejuhl and Kurpjuivut.[9] The results were judged by the _B. coli_ content, which was taken as an index of pathogenicity because this typical intestinal bacillus was found to be more frequent and less viable than the majority of the pathogenic organisms. Other important work on this subject was carried out, in connection with the pollution of the Hooghly River, by a Bengal Government Commission in 1904; and by the State Board of Health of Ohio in co-operation with the Bureau of Plant Industry of the United States Department of Agriculture in 1907. The chlorination experiments of the latter were reported by Kellerman, Pratt, and Kimberly.[10] The most valuable contribution to the disinfection of sewage was that of Phelps,[11] who critically examined the work of previous experimenters and directed attention to the unnecessary stringent standards adopted in European practice. His work at Boston in 1906, at Red Bank, N. J., and at Baltimore in 1907, demonstrated in an indubitable manner the economic possibilities of sewage chlorination. The dosages necessary for crude sewage and filter effluents were indicated and also the necessary contact periods. This work marks the commencement of a new era in sanitary science. The first occasion on which chlorine compounds were first used for the disinfection of water cannot be definitely ascertained. It has been stated to the author that bleach was used for treating wells as early as 1850 but this treatment was apparently made without definite knowledge of the destruction of micro-organisms. In 1897, Sims Woodhead employed bleach solutions for the sterilisation of the distribution mains at Maidstone, Kent, subsequent to an epidemic of typhoid fever.