To further avert all suspicion I find it a good plan to hand the necessary money to an inhabitant of the place and ask him to fetch me from the local shop the amount of alum or lime required. I then, if alum be chosen, tell him to pound it up with a brick and himself to throw it into the well, myself standing somewhat aloof. As everyone is familiar with the use of alum in purifying water, and there is obviously no possibility of the surreptitious introduction of anything else, with ordinary tact, no objection will ever be made. Of course, the person thus impressed into the service of sanitation should always be a man of good caste, preferably a Bhraman. Both these agents act, I believe, mechanically by coagulating certain forms of organic matter present in the water, and so carrying to the bottom, entangled with it, the germs present in the water, in which situation they perish on account of the free access of water containing their nourishment being impeded, and on this account at least two days should be allowed to elapse before the water is again taken into use, during which all disturbance of the water should be carefully avoided. Neither of these agents is in any degree as trustworthy as permanganate, but their employment should not be neglected in cases where the latter is either unobtainable or objections are raised to its use. Of the two, lime is probably the better, but alum much the handier. Whichever agent be adopted, it is well to treat as large a number of wells as possible. A certain number must needs, of course, be left untouched, for use during the time the treated wells must be left undisturbed, and these should be dotted about the town, so that the minimum of inconvenience may be inflicted on the townsfolk; but always leave as few as possible, as objections may be raised on your second visit, a couple of days after, to complete the process by disinfecting the remaining wells, and it may hence happen that you may have to rest content with what you have been able to effect on your first visit. Always, too, commence operations on the well you have reason to suspect is infected, or, in other words, that used by the people of the house in which the first local case has occurred.