It is much to be wished that some effectual plan may be soon discovered for ventilating sewers; and, although I do not profess myself competent to decide what direction such a discovery is likely to take, the most promising idea I have yet heard proposes the extraction of foul air by the action of fans placed in suitable localities, the present ventilators being retained in the capacity of inlets for pure air, instead of outlets for foul air; acting, in fact, like the down draught in a mine. We all know, by reading, what great lengths of galleries in mines deep below the surface of the earth are ventilated, and very efficiently, in this manner, and it seems not unreasonable to hope that the system may be found applicable to the purpose under consideration. Certainly, there seems no reason to doubt the almost illimitable power of steam fans to induce currents in any direction; and leaving the question to be worked out by those who are making a practical study of it, I can but wish them every success, believing an effectual system of sewer ventilation to be one of the chief sanitary _desiderata_ of the present day. WATER SUPPLY. The Report, by Professor Frankland, on the analysis of the waters supplied by the Metropolitan Water Companies during the several months of the year, is, on the whole, somewhat more favourable than usual. As regards “temperature,” he notices the wide variation in the waters derived from riverian sources, as compared with the narrow range in the deep well water of the Kent Company, derived from the chalk. The temperature of the Thames water varied from 36° Fahr. in February to 68°–9 in June, a range of 34°; while the range in the water of the Kent Company was only 7°–9 Fahr., viz., from 51–l° in May to 59° in September and October. The total solid impurities—composed of a great variety of substances, some of which are organic and very objectionable, and at times eminently noxious, while others are either entirely or comparatively harmless—was rather less than in previous years, the progressive increase in the quantity which had been noticed during the years 1871–2–3 having apparently ceased. The maximum was observed in January, and the minimum in July. The character of the Thames water, in respect of organic impurity—as represented by its two most important constituents, carbon and nitrogen—was practically the same as in the previous years. The maximum pollution occurred in March, April, and December, when the river was in a very objectionable condition. In December the Chelsea Company supplied this foul water in an unfiltered condition, and contaminated with fœcal matter. The subjoined table shows the maximum, minimum, and average quantity of organic matter in the water, the amount of organic element (organic carbon and organic nitrogen) in the Kent Company’s water being taken as unity, or the standard of comparison:—