84 THE ART AND PRACTICE OF LANDSCAPE GARDENING. 



line, and there are doorways, a fresh set of pipes should be arranged 

 between the doorways, otherwise the pipes should be placed below 

 the floor-line in a trench and covered by a grating when necessary. 

 Each house should have its own system of heating controlled by 

 valves from the main. The water should be able to rise to the 

 highest point of the heating pipes as soon as possible, and will thus 

 have less opportunity to cool. Pipes are generally in 9 ft. lengths, 

 with either flange ends, or spigot and socket ends. The first-named 

 are made tight with vulcanised indiarubber joints between the flanges, 

 which are bolted together. For the latter the best joint in under- 

 ground work is the rust joint, wherein the space between socket 

 and spigot is caulked with rope, and sealed with a mixture of damp 

 iron filings and sal ammoniac. Above the ground the joints may be 

 made tight by indiarubber rings. Boilers vary much, according to 

 different makers. There are very good ones which are most suitable 

 to the class of work for which they are required. The most 

 effective boiler is that which has a large surface horizontally above 

 the flame ; vertical surfaces above the flame are reckoned to have 

 half the efficiency of the horizontal surface. Horizontal surfaces 

 below the flame are not valued at all. Every square foot of 

 effective heating surface is reckoned to heat 40 ft. of 4 in. pipe. 

 Coke is the best and most economical heating material. If wood 

 be used, a large grate area is necessary. Clean rain water should 

 always be used for the boilers. It is advisable in a large range to 

 have two boilers, connected or disconnected at will, each one capable 

 of heating the range. It is more economical to have an excess of 

 boiler power and piping than is theoretically required, and to work 

 at a low pressure, than to work a smaller system at a high 

 pressure. Water expands in the boiler about one-thirtieth of its bulk, 

 so the supply cistern should be fixed a slight distance above the 

 level of the highest point of the system and connected with the 



