And although, as one of the experts to whom Chadwick appealed and whose moderate testimony was cast aside because it did not come up to the standard desired by his enthusiasm, I fully endorse Mr. Spencer’s caution with regard to the mass of Blue Book evidence on sanitation, I venture to express my regret that the dear old man has had an unfortunate experience of sewage treatment, and my surprise that so deep a reasoner should have published his judgment in this chapter without having taken the pains to extend his acquaintance with sewage treatment in other places than the single instance of Burton-on-Trent. In thus despising an unsavoury subject Mr. Spencer is not alone, and I am sorry to have to say that general indifference is answerable for the waste of much public health and money, because it need not be surprising if those following a _despised_ trade are sometimes ready to take advantage of the prejudice and ignorance of their employers. In this sense I beg to quote Professor Spencer as follows in justification of the reflection with which I began the above essay:— “New sanitary appliances are continually being devised, sanctioned by authority, and required by surveyors; and surveyors may have and certainly sometimes do have, personal interests in pushing the use of them; either as being shareholders in the companies they are manufactured by or as receiving percentages on the numbers sold through their recommendation.” [2]: Published by Longmans, London, 1874. Third edition published by R. Potter, Wrexham, 1885. [3]: ‘Facts and Comments,’ by Herbert Spencer. Williams and Norgate, London, 1902. NATURAL AND ARTIFICIAL SEWAGE TREATMENT. BY H. ALFRED ROECHLING, M. INST. C.E., ETC. I. INTRODUCTORY REMARKS. At the request of Lieut.-Colonel A. S. Jones, V.C., Assoc. M. Inst. C.E., who has done yeoman service in this matter, I have great pleasure in putting down some observations on this old but ever controversial question of sewage treatment.