In level ground, the problem of finding a suitable outlet is a serious one, and in many cases impossible of solution, so that the householder, being unable to find an outlet, must put up with the ground water and be as patient as possible during its prevalence. It does not do to trust one's eye to find a practicable outlet, since even a trained eye is easily deceived. An engineer with a level can tell in a few moments where a proper point of discharge may be found, and it is absurd to begrudge the small amount which it will cost, in view of the large expense involved in digging a long trench to no purpose. Some years ago the writer was able to note the conditions in a house where the cellar excavation went three feet into limestone rock. The strata were perfectly level and the cellar floor of natural rock was apparently all that could be desired, smooth and flat, without involving any expense for concrete. One wall came where a vertical seam in the rock existed, and since this natural rock face was smooth and vertical and just where the cellar wall should go, it seemed unnecessary to dig it out and lay up masonry in its place. So it was left and the house built. When the spring rains came, however, the cellar was turned into a pond, water dripping everywhere from the vertical rock face, and coming up through the cellar bottom like springs. It cost a great deal more then to make the changes and improvements necessary in order to secure a dry cellar than it would have done at the outset. This serves as an illustration of the need of taking every precaution at the beginning to insure a dry and well-drained soil around and below the cellar walls. CHAPTER III _CONSTRUCTION OF HOUSES AND BARNS WITH REFERENCE TO HEALTHFULNESS_ Any liability to disease that may come from faulty construction of habitations is likely to spring from a polluted subsoil. Such pollution vitiates the air drawn from that soil and is a source of danger on account of the resulting impurity of the whole atmosphere within the house. _Shutting out soil air._