These are constructed in two ways, either as water-tight receptacles or as simple pervious pits differing in no way from the privy vault excepting, perhaps, in their more dangerous tendencies. All sanitary authorities agree in condemning the leaky cesspool as a most shiftless and dangerous method of getting rid of sewage. In most countries they are prohibited by law in populous communities. In exceptional cases, leaky cesspools may do no harm, as in an isolated house in the country whose cesspool is built at a considerable distance both from the house and the well. The safe distance from any well it would be difficult to state, because that would depend on the character of the subsoil and the general slope of the land. In any case, the cesspool should be on lower ground than the well, as the current of the ground water feeding the latter, usually but not always, conforms to the slope of the surface. A fair estimate of the least allowable distance between well and cesspool would be 100 feet. Soluble salts from sewage might still find their way into the well water, but it is quite improbable that disease germs could penetrate the soil for such a distance except where fissures and cracks may be present. [Illustration: Fig. 2.--Portable earth closet. A, the pail to receive the excrement; B, the urine-separating receptacle hanging on the open door; C, mouth of the hopper conveying the dry-earth or ashes from reservoir D upon the night soil in A.] In villages, leaky cesspools are still of frequent occurrence. If the drinking water is taken from wells, such cesspools are a constant menace, and all that is needed in many such towns is a spark in the shape of some disease germ to kindle an epidemic. It is true that years may pass by without the occurrence of more than the usual amount of illness, but even then we have good reason to suppose that in many villages using cesspools the average amount of sickness and mortality is far too high, not to mention the occasional epidemics of typhoid-fever. We may sum up the matter of leaky cesspools by the statement that they may do no harm near isolated houses on farms, provided they are sufficiently far away from the source of water-supply. In small towns cesspools should be prohibited, or only very thoroughly constructed water-tight ones permitted, according to circumstances. The same holds true for the well-known privies.