Mr. W. J. Dibdin advised the construction of filters or fine grained bacteria beds. Two beds having a combined area of a quarter of an acre and a capacity of 200,000 gallons, were built in 1895–96 for the purification of the chemically treated sewage. In 1896 the first bacteria bed was constructed for the treatment of crude sewage. As previously stated, many tests were made to determine the best kind of material for filling the beds. The crude sewage, after being screened to intercept floating matter, is run directly onto the filters without the addition of any chemicals. After remaining in the beds for a period of two hours the effluent is in a fit condition to be discharged into the brook leading to the Thames and is uniformly superior to the effluent obtainable by local land treatment. All experiments with bacteria beds show that the objects for which they were intended, to abolish sludge, has been realized and that sewage can be purified without chemicals at a small cost, being but little more than that incurred by the labor in attending to, or supervising the filling and discharging, the filters, and that sewage purification can be carried on with little or no nuisance. _Discussion_ The amount of purification to be obtained by dilution depends upon the size of the stream into which the sewage is discharged and also upon the amount of oxygen contained in the stream. The latter condition is controlled very largely by the rate of flow of the stream and its previous condition of pollution. Mr. E. P. Stearns in his report to the Massachusetts State Board of Health, 1890, on Pollution and Self-Purification of Streams, gave a table showing the calculated amount of free ammonia, dissolved solids and chlorine which sewage adds to running streams. Much interest is being taken in the effect of the discharge of the sewage of Chicago, and the waters of Lake Michigan, into the Illinois River, and the outcomes of the analyses of samples taken along the river is awaited with interest. Published reports have not been given out, but information from the most reliable sources seem to show that a considerable purification takes place in the passage down the river. No reliable data could be obtained giving the percent of purification by irrigation. At Berlin the sewage is purified by this method, and the effluent comes well within the requirements of the German law. With chemical treatment about 90 percent of the matter in suspension and a small percent of that in solution is removed, and the purification is about 53 percent of the total organic matter. The best examples of intermittent downward filtration show an efficiency of 95 percent on the total organic matter. However, if this process is used in connection with other methods the organic matter may be reduced 99 percent and the chemical analyses of the effluent may fill the drinking water requirements.