1. To have pure air, your house must be so constructed as that the outer atmosphere shall find its way with ease to every corner of it. House architects hardly ever consider this. The object in building a house is to obtain the largest interest for the money, not to save doctors' bills to the tenants. But, if tenants should ever become so wise as to refuse to occupy unhealthily constructed houses, and if Insurance Companies should ever come to understand their interest so thoroughly as to pay a Sanitary Surveyor to look after the houses where their clients live, speculative architects would speedily be brought to their senses. As it is, they build what pays best. And there are always people foolish enough to take the houses they build. And if in the course of time the families die off, as is so often the case, nobody ever thinks of blaming any but Providence[8] for the result. Ill-informed medical men aid in sustaining the delusion, by laying the blame on "current contagions." Badly constructed houses do for the healthy what badly constructed hospitals do for the sick. Once insure that the air in a house is stagnant, and sickness is certain to follow. [Sidenote: Pure water.] 2. Pure water is more generally introduced into houses than it used to be, thanks to the exertions of the sanitary reformers. Within the last few years, a large part of London was in the daily habit of using water polluted by the drainage of its sewers and water closets. This has happily been remedied. But, in many parts of the country, well water of a very impure kind is used for domestic purposes. And when epidemic disease shows itself, persons using such water are almost sure to suffer. [Sidenote: Drainage.] 3. It would be curious to ascertain by inspection, how many houses in London are really well drained. Many people would say, surely all or most of them. But many people have no idea in what good drainage consists. They think that a sewer in the street, and a pipe leading to it from the house is good drainage. All the while the sewer may be nothing but a laboratory from which epidemic disease and ill health is being distilled into the house. No house with any untrapped drain pipe communicating immediately with a sewer, whether it be from water closet, sink, or gully-grate, can ever be healthy. An untrapped sink may at any time spread fever or pyaemia among the inmates of a palace. [Sidenote: Sinks.]