On the contrary, when the water in a brook flows through a meadow used for pasture or through gullies, the sides of which are manured, or in the vicinity of houses and barns, the water is probably unfit for drinking purposes. This can be realized by standing at the edge of a barnyard and watching the rain falling first on the roof of the barn, then in larger quantities from the eaves on to the manure pile into the yard below, then accumulating in pools of reddish black concentrated liquid, until the volume is sufficient to form small rills which gradually assemble into a fair-sized stream. Similarly, the pig-pen drainage is washed out from under or even through the building, and, after combining with the barnyard drain, is carried into the stream near by. The very idea of drinking such filth is nauseating in the extreme. It is common for small slaughter-houses to be built on the side of a stream, so that the offal, carrion, and refuse of the place may be carried off without effort on the part of the owner, and there are a number of such places where brooks, used as places of deposit for slaughter-house refuse, discharge directly into the reservoirs of water works. But this sort of animal refuse is not the most serious pollution. The leachings and washings from privies and cesspools, carrying, as they do, germs of contagious diseases, are most to be dreaded, and when a privy (with no vault underneath) is built on the side of a steep ravine and is so located that the natural drainage of the sidehill on which it is built cannot help but run around and through the building, then the pollution of the stream in the gulley is not only direct and inevitable, but of a deadly sort (see Fig. 36). Fortunately, the germs thus carried into the stream suffer the vicissitudes of all life exposed to the attacks of hostile forces. At the time of freshets the streams carry mud in abundance, which mud is continually settling out of the water as opportunity offers, and with this settlement of mud there occurs also the settlement of the germs. Also the pathogenic or disease-producing germs are usually weaker and more susceptible than the putrefactive and other organisms which are found in the water in great abundance after any rain storm, and which tend to inhibit or destroy the pathogenic germs. But some will survive, and, with favoring conditions, may pass through the water-pipe to the house, causing sickness, if not death. [Illustration: FIG. 36.--Stream draining a privy.] Any inspection of the watershed, therefore, should look to the elimination of the dangers above described, and to the location of barns and barnyards, pig-pens and poultry yards, privies and cesspools, so that no direct drainage into the stream shall be possible.