0.55 inch in 5 minutes.

1. 50 inches in 45 minutes.

1.10 inches in 15 minutes.

1 -80 inches in 60 minutes.

1 25 inches in 30 minutes.

2.20 inches in 120 minutes.

It is by no means rare (and it is within my own knowledge) to have a fall of

1 inch in half an hour. So that it will be safe to take an extreme case of, say,

2 inches falling in 1 hour. As it is usually impossible to pass this rainfall away by any other method than the drain, or to have any system of relief or storm-overflow drains, the house-drain must serve this purpose, and although some small portion may by soakage and evaporation not reach the drain, this portion - having regard to the impervious character of the surfaces of the roofs and yards, and the rapidity with which rain falls during violent storms - may be neglected. It used to be the custom to make an allowance also for a certain amount of subsoil-water finding its way into the drains, the joints of which were purposely left open to facilitate its entrance, but joints which let water in, also lot sewage out, and thus set up a dangerous condition of things by the pollution of the soil. The realization of this fact, coupled with the necessities of keeping out surface or ground water as far as possible, as referred to above, has led to drains being constructed with absolutely water-tight and air-tight joints, so that they may more efficiently perform their functions as conduits for sewage and foul waters, the speedy removal of which from the house and its precinets is one of the most essential conditions necessary to the maintenance of a healthy habitation.

Before laying down any code of regulations to ensure efficiency in a drainage system, it will be well to consider what are the dangers and defects to be avoided. The removal of domestic sewage is either effected by the water-system, or by the conservancy system, which includes "privy-midden" closets, "pail" and "earth" closets. In the conservancy system, the faeces are kept out of the drains, which receive only the foul waters of the house. Very many people remain under the impression that, with a conservancy system, the question of drainage is of little importance, as they imagine that what the drain has to convey away is not of a dangerous character; hut when we come to add to the ordinary waste waters of the house, the chamber-slops containing the urine and in some cases the sewage from stables, cow-houses, and piggeries, it will be at once Been that we have a highly-complex liquid, and one which differs in its impurity only to a slight degree from the sewage containing also the discharge- from water-closets.1

Decomposition of sewage begins directly it passes into the drain, and may be said to reach its most active stage after the lapse of from three to four days, though in some states of the atmosphere the time is longer. Often very fetid substances are given off, and the following gases have been traced: - Sulphuretted hydrogen (H2S), marsh gas (CH4). bicarburetted hydrogen (C2H4), carbonic acid gas (CO,) in excessive quantities, and ammoniacal gas. Having regard, therefore, to the dangerous character of sewage, it is important that the system of drainage, devised for removing it from the precincts of the house, shall be free from defects attributable to bad design, unsuitable materials, and careless workmanship.

The only drainage-system to many houses consists of a series of stone or brick drains of rectangular form, the materials being laid with open joints. While this type of drain may be the most suitable for drying the ground, it is the most unsuitable for conveying sewage, which is invariably deposited upon the flat bottom, and percolates through the open joints into the surrounding soil, and the gases given off may be drawn through the soil into the house, or escape by way of the connections and imperfect sanitary appliances into the house. In many instances, this particular type of drain was originally laid down for the purpose of draining away the water found in the site, and is frequently found under basements of houses. From time to time, as sanitary appliances have teen added to the house, the several waste-pipes have been connected to the drain, until gradually it has become filled with sewage-deposit, and a huge underground reservoir of sewage-gas is formed.

1 8ee Vol. II. Section IX.page 4.

Another very objectionable type of drain is that formed of egg-shaped earthenware pipes with "butt" joints, - that is, an open joint without any overlapping sockets, - which allow the percolation of the sewage into the soil and the escape of gas; and, in addition, this want of joint facilitates deposit in the pipe by reason of the readiness with which any Moating object gets locked in the opening between the pipes, and so forms an obstruction.

The material now most generally used for house-drains is the circular socketed earthenware pipe, but it will not do to assume that, ticca use the drain is of this material, it is therefore quite right. A drain formed with such pipes may be extremely defective, because of their unsoundness, bad shape, and want of proper jointing, as well as on account of imperfect foundation, and not being laid true to the gradient or alignment, any of which defects will surely cause the drain to Income a nuisance.

One of the greatest defects to be avoided is bringing a drain inside a house. It is rare indeed that any necessity arises for such a course, yet it is very common to find basements plentifully supplied with gullies, and investigation reveals that the only purpose they serve is to carry away the water used in washing the floors. Here we have a communication between the interior of tin-house and the sewer, the only check being the trap in the gully, which may or may not be an efficient one; and even if it is so theoretically, it must be remembered that it will lose its seal by evaporation, and that the water standing in it will absorb the gas coming from the drain, and give it off into the house. It is a common thing to receive an assurance that all the drains about a house are properly trapped, the special faculties of a trap being understood by some people to be almost supernatural; but an interior trap, however good in form, without external disconnection, can never be anything but a defect, and any system which includes waste-pipes, whether trapped internally or not, which have a direct connection with the drain, is one to be avoided.