The water column piping should be examined and known to be free and clear. The water level, as indicated by the gauge glass, should be checked by opening the gauge cocks. The method of drying out a brick setting before placing a boiler in operation is described later in the discussion of boiler settings. A boiler should not be cut into the line with other boilers until the pressure within it is approximately that in the steam main. The boiler stop valve should be opened very slowly until it is fully opened. The arrangement of piping should be such that there can be no possibility of water collecting in a pocket between the boiler and the main, from which it can be carried over into the steam line when a boiler is cut in. In regular operation the safety valve and steam gauge should be checked daily. In small plants the steam pressure should be raised sufficiently to cause the safety valves to blow, at which time the steam gauge should indicate the pressure at which the valve is known to be set. If it does not, one is in error and the gauge should be compared with one of known accuracy and any error at once rectified. In large plants such a method of checking would result in losses too great to be allowed. Here the gauges and valves are ordinarily checked at the time a boiler is cut out, the valves being assured of not sticking by daily instantaneous opening through manipulation by hand of the valve lever. The daily blowing of the safety valve acts not only as a check on the gauge but insures the valve against sticking. The water column should be blown down thoroughly at least once on every shift and the height of water indicated by the glass checked by the gauge cocks. The bottom blow-offs should be kept tight. These should be opened at least once daily to blow from the mud drum any sediment that may have collected and to reduce the concentration. The amount of blowing down and the frequency is, of course, determined by the nature of the feed water used. In case of low water, resulting either from carelessness or from some unforeseen condition of operation, the essential object to be obtained is the extinguishing of the fire in the quickest possible manner. Where practicable, this is best accomplished by the playing of a heavy stream of water from a hose on the fire. Another method, perhaps not so efficient, but more generally recommended, is the covering of the fire with wet ashes or fresh fuel. A boiler so treated should be cut out of line after such an occurrence and a thorough inspection made to ascertain what damage, if any, has been done before it is again placed in service. The efficiency and capacity depend to an extent very much greater than is ordinarily realized upon the cleanliness of the heating surfaces, both externally and internally, and too much stress cannot be put upon the necessity for systematic cleaning as a regular feature in the plant operation.