Of course, when the aerobic treatment is carried out on a bare level surface of cinders or coke growing only weeds, the lack of interest is very excusable, but in the natural system the growth of crops and contouring a sloping surface with carriers so that every part shall have its trickling water alternating with dry periods for cutting the crops or hoeing out weeds, should be a matter of constant interest to an agricultural worker, and, if he knows his business, good crops and purity of effluent must go together. [Sidenote: Managers should have a free hand.] In order to attain this happy result, a manager must know his business and be given a free hand, not pestered by members of a committee (farmers, butchers, gardeners or town tradesmen) coming to give their advice or orders. The river authority should take samples as often as they like and send the manager as soon as possible the analyses with day and hour of sampling as a guide for future working. He will then have to explain any defect from average purity of effluent, due to one of the hundred contingencies which may arise in practice, after he and the river authorities have agreed about what that average analysis should be for his particular farm or works; and it will be for the advantage of all parties not to try and enforce a fixed standard for a whole district, as some river authorities usually attempt to do, because it is easier to lead than to drive a good manager, and nothing at all can be done with a bad one. It must not be supposed that I think river authorities should be easy going, quite the contrary, but they should trust their inspectors’ reports, and “run in” those sanitary authorities who are careless about the management of their sewage farms and trying to cut down working expenses and capital. In precipitation or other artificial sewage works it is easy to judge this, but more difficult for any one except the good farm manager to know whether the land is being made the most of for profit or for purification; still the rivers authority ought to get to know if they and their officers take pains. [Sidenote: Purification and profit.] It is a common idea that working a sewage farm for profit, and for purification of the sewage, are two incompatible things, whereas, the good manager with sufficient working capital (double or more what would be enough for the same acreage in ordinary agriculture) and a good market for produce will attain the two together in due proportion in all ordinary seasons, when a fair allowance has been made him for the necessary sanitary work.