Most houses in connection with a large brick sewer have a “flap-trap,” just where the house drain enters into the sewer; this flap opens to allow the house sewage to enter the sewer, whereupon it should immediately close again to exclude foul air and rats from invading the house. They sometimes, however, do not shut closely, and in that case their action for good is almost at an end. A householder can have an occasional inspection made of the trap by the sewer men, by paying a small fee to the vestry. _Precautions after Floods._--Dwellings which have been invaded by the waters should receive special care, so that those whom the flood has expelled should not occupy them before they have been made sufficiently healthy for habitation. They should first be cleaned out as quickly and thoroughly as possible, and freed from all dirt and debris deposited in different parts by the water. Continuous aëration and the most active ventilation are the best and most energetic agents. To increase these as much as possible, where it can be done, a large fire should be maintained on the hearth, and the doors and windows opened, so that the light and heat of the sun may contribute their part to purifying the air. At the same time care must be taken to dig a ditch 10-15 in. deep around each house, whose interior is in many cases below the level of the ground. It will also be well, after having torn down all plastering, which will be in a bad condition, to scrape to their bottom all joints in the walls, and to replaster them in the parts of the house most injured, and where bad deposits have principally accumulated. The floors, where such exist, should be carefully attended to, and the soil under them covered with a disinfecting substance, such as pounded charcoal, or sand, or else with an impermeable material, such as flagging, paving blocks, cement, &c. Where the house is several stories high, the top stories should be the first occupied.