With respect to the question of circulation of air in sewers, plus ventilation, I may mention that a striking illustration of the value of this plan was afforded in the locality of Notting Hill Square. At one of the houses at the southern, or loftiest side of the square, there had been numerous cases of fever, and there was clear evidence of the escape of sewer gas into the house in question. Upon careful enquiry into the drainage of the locality, 1 ascertained that the sewer which received the house drainage originated in a dead or blind end, and that the ventilation was insufficient. Your Vestry directed a communication to be made between the blind end in question and another very near to it, thus setting up a free circulation in the system; and at the same time freely ventilated the sewer near the junction. The effect was everything that could be desired: for certain improvements in respect of the trapping and ventilation of the house drains having been carried out, the evil complained of was effectually removed, and no farther illness has been reported.

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:—

Name of Company. Maximum. Minimum. Average.
Kent 1.0 1.0 1.0
West Middlesex 4.3 2.0 3.0
Grand Junction 4.9 2.4 3.3
Chelsea 7.1 2.3 3.7

Professor Frankland remarks that the water of the Thames is at its source as free from pollution as the chalk well water, but on its downward course becomes largely and progressively contaminated by sewage and the washings of cultivated land, especially during winter.

The average hardness of the Thames water—or the weight of carbonate of lime, or its equivalent of other soap-destroying substances, found in 100,000 parts of water was 21° or parts in 1873, and 19.7° in 1874. Large quantities of soap or soda are required to soften the water before it is used for washing; but this process could be accomplished for a small portion of the expense by substituting lime for soap or soda, as practised on similar waters at Aylesbury, Canterbury, Caterham, and Tring. The following table exhibits the degree of efficiency of filtration of the waters:—

Name of Company. No. of occasions
when clear and
transparent. 		No. of occasions
when slightly
turbid. 		No. of occasions
when turbid. 		No. of occasions
when very
turbid.
Chelsea 6 5 0 2
West Middlesex 12 1 0 0
Grand Junction 7 5 1 0

The exceptional occasion on which the water supplied by the West Middlesex Company was slightly turbid was in December, when the condition of the Thames was bad for a lengthened time, so that even the large storage of the Company proved insufficient to render them independent of flood water; it being impossible, moreover, to separate by filtration the whole of the finely divided clay to which the turbidity of the water was due. The Kent Company’s deep well water, having already undergone natural filtration through an enormous thickness of chalk, is always clear and transparent, without artificial filtration. The appliances of the Companies supplying river water are, excepting in the case of the West Middlesex Company, unequal to the filtration work required of them. The microscope is called into use in the examination of potable water, and it always reveals numbers of living and moving organisms in the sediment deposited by turbid water on standing. The annexed table exhibits the results of such microscopic examinations during the past six years:—

Name of Company.

Number of occasionswhen living
organisms were found.

1869.

1870.

1871.

1872.

1873.

1874.

Chelsea

3

2

2

3

2

5

West Middlesex

0

0

0

0

0

0

Grand Junction

4

1

1

2

3

5