before mentioned, or where necessary by carrying up the inlet by means of a ventilating pipe to above the roof.  The inlet should be equal in area to the drain pipe, and not in any case less than 4 in. in diameter.  If it were not for appearance and the difficulty of conveying the excreta without lodgments, an open gutter would be preferable to a closed pipe in the house.  This arrangement is based on the principle that there should be no deposit in the house drains.  Therefore the utmost care should be taken to lay the house drains in straight lines, both in plan and gradient, and to give the adequate inclination.

The following are desirable conditions to observe in house drains:  1.  As to material of pipes.  House drains should be made either of glazed stoneware pipes or fireclay pipes with cement joints, or preferably of cast iron pipes jointed with carefully-made lead joints, or with turned joints and bored sockets.  I say preferably of cast iron.  In New York the iron soilpipe, with joints made with lead, is now required by the municipal regulations.  It is a stronger pipe than a rainwater pipe.  The latter will often be found to have holes.  A lead joint cannot be made properly in a weak pipe, therefore the lead joint is to some extent a guarantee of soundness.  Lead pipes will be eaten away by water containing free oxygen without carbonic acid, therefore pure rainwater injures lead pipes.  An excess of carbonic acid in water will also eat away lead.  You will find that in many cases pinholes appear in a soilpipe, and when inside a house that allows sewer gas to pass into the house.  Moreover, lead is a soft material; it is subject to indentations, to injury from nails, to sagging.  A cast-iron pipe, when coated with sewage matter, does not appear to be subject to decay; and if of sufficient substance it is not liable to injury.  When once well fixed, it has no tendency to move.  I would, therefore, advocate cast iron in lieu of lead soilpipes.  In fixing the soilpipe which is to receive a water-closet, the trap should form part of the fixed pipe; so that if there is any sinking the down pipe will not sink away from the trap.  It is, however, not sufficient to provide good material.  There is nothing which is more important in a sanitary point of view than good workmanship in house drainage.  In this matter, it is on details that all depends.  Just consider; the drain pipes under the best conditions of aeration contain elements of danger, and those pipes are composed of a number of parts, at the point of junction of any one of which the poison may escape into the house.  You thus perceive how necessary it is first to reduce the poison to a minimum by cutting off the sewer gas which might otherwise pass from the street sewer to the house drain, and in the next place being most careful in the workmanship of every part of your house drains and soilpipes.  Reduce your danger where you can by putting your pipes outside.  But you cannot always do that—­for instance, at New York and in Canada they would freeze.