VALVES. In all heating arrangements by hot water, Valves are requisite for regulating the passage of heat to different houses and pits, and for shutting it off altogether from any part when not required. The ordinary kind, which can easily be opened or closed with one hand, answers very well for the mere purpose of regulating heat. A high-pressure Valve, the aperture in which is opened and closed by means of a screw and thread, is sometimes put in near the boiler when there is more than one main, or when two boilers are connected for working both together and separately. When these Valves are screwed down, the water cannot circulate or pass, and this is of great advantage in case of repairs being necessary to one of the boilers, as the other can meanwhile be kept at full work. High-pressure Valves are not required on all boilers, but sufficient of the ordinary kind should be introduced where necessary to insure the apparatus being worked readily and the regulation of heat kept under easy control.