Mr. Binnie. spaces, he considered that no apprehension need be felt on this score, as percolation-beds of this type-for example, those at Cohmbus, Ohio-worked perfectly well a t temperatures very much lower than any which obtained in England. The question whether the degree of dilution affected the amount of filtering-material which should be employed was a very interesting one, and he considered that the experience a t Salisbury rather tended to endorse the view put forward by Mr. Martin. With regard to Mr. Jenkin's question whether the 7-inch pipe to which Fig. 6, Plate 7, applied had burst, as it was under a head of 47 feet, the Author would be very surprised to learn that this had happened. It was true that the difference in level between the two ends of the sewer was 47 feet, and therefore if the lower end of the sewer were blocked, all the intermediate manholes closed, and the pipe filled with water, it would be possible to put the lower end under a head of 47 feet : these, however, were conditions which hardly obtained in practice, as the static head was entirely converted into kinetic energy, so that there could be little or no static pressure on the inside of the pipe. With regard to the discrepancy pointed out by Mr. Jenkin between the total flow of crude sewage to the air-lift pump and of the effluent from the percolation-bed in the 24 hours in Tables I and 11, Mr. Jenkin appeared to have overlooked the foot-note to Table I, which stated that at 9 . 5 0 a.m. five beds were at work, and that the effluent from one of them was not measured. This would account for part of the discrepancy and would bring the figures as near as it was possible to get them within the limits of accuracy attainable by measuring the depth of discharge over the weirs. I n conclusion, he wished to thank Colonel Harding for his valuable contribution to the discussion, with which he thoroughly agreed.Correspondence.. Mr. Anderson.Mr. J. T. NOBLE ANDERSON remarked that it was evident the Authors of the two Papers had attained a measure of success remarkable even in England. Consideration of similar works abroad, and of their history, led him, however, to question the opening quotation made by Mr. Watson, that England's lead in such things was due to her necessity. I n America, and even in the sparsely populated Australian colonies and New Zealand, circumstances and Downloaded by [ University of Sussex] on [16/09/16].

The President. especially qualified to speak on the subject of the prevention of pollution by trades waste, because his professional avocations brought under his inspection a great many manufactories. But however desirable it was to prevent the pollution of streams, it was necessary to be careful not to harass the manufacturers to such an extent as to ruin their trade. Manufacturers often had but a small margin of profit, and were in competition with foreigners who were not subject to the restrictions which obtained in England. Happily the utilization of trades waste sometimes led to profit. An admirable instance of the profits arising from trades waste might be found in gasworks. I n former days the tar and ammoniacal liquors had been got rid of as best they might be, with no thought of utilizing them. Now those refuse products were a great aid in lowering the price of gas.

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