=Steam Radiator Valves.=--Like most other mechanical appliances that are extensively used, radiator valves are made by a great number of manufacturers and in many different forms. Some possess special features that are intended to increase their working efficiency but the type of radiator valve most commonly used for ordinary construction is that illustrated in Figs. 14 and 15. It is a style of _angle valve_ that takes the place of an elbow and being made with _a union joint_, also furnishes a means of disconnecting the radiator without disturbing the pipes. Fig. 14 is an outside view of the valve and Fig. 15 shows its mechanical construction. The part _B_ screws onto the end of the steam pipe and _A_ connects with the radiator. The part _C-D_ is the _union_. The nut _C_ screws onto the valve and makes a steam-tight joint at _D_, between the parts. In case it is desired to remove the radiator, it furnishes an easy means of detaching the valve. The composition valve-disc _E_ makes a seat on the brass ring directly under it, to shut off the steam. In case the valve leaks, the disc may be removed by taking the valve casing apart at _G_. The worn disc can then be replaced with a new one which may be obtained from the dealer who furnished the valve. The only moving part of the valve exposed to the air is at the point where the valve-stem _S_ enters the casing. The joint is made steam-tight by the packing _P_. The packing is greased candle wicking that is wound around the stem and held tightly in place by the screw-cap _H_. If the valve leaks at this joint, a turn or two with a wrench will stop the escape of the steam. THE HOUSE-HEATING STEAM BOILER House-heating boilers were formerly made of sheet metal and are still so constructed to some extent, but by far the greater number are now made of cast iron. Sheet-metal boilers are constructed at the factory, ready to be installed, but the cast-iron type is made in sections and assembled to make a complete boiler, at the time the plant is erected. Sectional boilers are convenient to install, on account of the possibility of handling the parts in a limited space, that would not admit an assembled boiler without tearing down a part of the basement for admission.