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320 they should be given a fair chance to do their work by giving them plenty of air. Where a closet is only three or four feet from the soil-pipe, this ventilation is not necessary for keeping the pipe clear; but it is more than ever necessary to prevent siphonage. It is only under such circumstances that I would use a trap specially difficult to siphon and without ventilation; but such a trap should be cleansed every six months, for a trap which will not siphon will collect filth.

8. Whether the work be for construction or for repair, see that skilled workmen are employed upon it. There is little difficulty in finding in any large city a plumber who understands his business and takes pride in doing good work. He probably will not compete for contracts, and his prices may be from twenty to fifty per cent higher than some other plumbers will demand; but it is wisest to employ the best men, accept their advice, and not grumble about their bills. A competent sanitary engineer, by which is meant a well-educated engineer who has made a special study of water-supply, sewerage, house-drainage, etc., will make the best drawings and specifications, but first-class workmen are required to carry these out; and a class of plumbers is slowly being developed who can make plans and specifications satisfactorily, and whose advice as to fixtures, etc., can be relied upon, and such men should be sought for and employed, no matter what their prices may be.

House-drainage may also be considered from the point of view of the man who wants to know whether the plumbing actually in his house is in such condition that it is or is not worth while for him to make changes or repairs in it. It may not be such a system as he would put in if he were building a new residence; but he does not wish to incur more expense connected with it than is absolutely necessary. If no offensive odors have been perceived, and there has been no sickness in the house which would give rise to a suspicion that the drains might be out of order, he will usually be satisfied, and will not even take the trouble to carefully examine the apparatus, and still less will he be disposed to have it inspected and tested by an expert. If offensive odors are perceived in the house, and cases of disease occurring in it have roused suspicion in his mind, he will probably be more inquisitive; and, if the physician advises skilled inspection, he will usually be willing to have this made. The essential points to be determined by such an inspection are, first, whether there is leakage from any part of the soil-pipe beneath the cellar or basement; second, whether there is any obstruction to the flow of sewage to the sewer; third, whether there is any leakage of gas into the house from any joint or fixture; and, fourth, whether the soil-pipe is properly ventilated and the traps properly