THOUGH I consider it highly unbecoming for one member of a committee, charged with an important inquiry, to criticise publicly and in a controversial nsanner, views expressed by another member of that committee in regard to the subject it has to investigate, still some of the remarks made by Mr. Hope at the Society of Arts last Wednesday seem so unmistakeably to refer to the article which appeared in NATURE on the 23rd December last, that I feel constrained, as the writer of that article, to reply to them. The statement objected to by Mr. Hope was an expression, not of individual opinion, but of the fact—long accepted as beyond question—that the practical value of liquid town sewage as manure, that is to say, its value to the farmer, cannot be computed solely from the amount of manure material it may contain, and that, in forming such an estimate, the positive element afforded by chemical analysis must be controlled by the negative element introduced by extreme dilution, and varying under different local circumstances. This fact has been recognised by authorities too numerous to name, and so decisively, that Mr. Hope's assertion as to the value of the ammonia in sewage being affected only in a very minor degree by the amount of water mixed with it, seems to have no other merit than that of being “sensational.” I am at a loss to conceive what ground Mr. Hope could have for objecting to the statement that “it is a great mistake, and likely to prove a very ruinous one,” to estimate the value of dilute sewage by calculation solely from the amount of manure material it may contain. Yet this is what Mr. Hope characterises as a “strange paradox.” Why it has puzzled him, as he admits, I will not stop to inquire; but I must protest against his representing “the obligation of applying water to crops at all times of the year, whether they want it or not,” as having been one of the reasons given for the statement he objects to. In doing that he has at least fallen into a great error, and he has at the same time evaded the point to which attention was directed in tbe article, viz., the agricultural difficulty attending the “continuous daily application of sewage to land.” That is a difficulty not to be disposed of ex cathedra—it would obtain whether the land destined to receive sewage were under crops or lying fallow. In the one case the application of sewage might be inadmissible during great part of the year; in the other case the land under fallow would be unproductive meanwhile. Indeed the need for applying sewage to fallow land, which Mr. Hope seems to suggest, would enhance the difficulty of disposing of sewage by irrigation, since it would involve the want of a still larger area of land for its reception, day by day throughout the year. Such a mode of application usight well necessitate an area of twenty-five acres for every 100 persons, and that necessity, if it existed, would be, I imagine, a very serious matterin the case of ninny towns.