STEAM VS. HOT WATER. 43 



3. The heat from steam distributes itself over a great 

 length of pipe more readily than that from hot water, and 

 steam, therefore has a distinct advantage for heating long 

 runs. 



4. Steam is preferable to hot water for irregular and 

 crooked circuits. 



5. Unfavorable conditions of piping can be more readily 

 overcome with steam than with water. 



6. The addition of crooks and angles in pipes is deci- 

 dedly disadvantageous to the circulation of hot water t 

 and of steam without pressure ; but the effect is scarcely 

 perceptible with steam under low pressure. 



7. In starting a new fire with cold water, circulation be- 

 gins with hot water sooner than with steam, but, in ordina- 

 rily long runs, it requires a longer time for the water to 

 reach a point where the temperature of the house is ma- 

 terially affected than for the steam to do so. 



8. The length of pipe to be traversed is a much more 

 important consideration with water than with steam, for 

 the friction of the water upon the pipe is much greater than 

 the friction of steam, and a long run warms slowly with 

 water. 



9. It is necessary to exercise greater care in grading pipes 

 for water heating than for steam heating. With steam, a 

 satisfactory fall towards the boiler is much more important 

 than the exact manner of laying the pipes. 



10. In heating by water in closed circuits, a high expan- 

 sion tank may increase the efficiency by allowing the water 

 to become hotter throughout the system, and probably by 

 giving a better circulation. 



Piping. The arrangement of the pipes must be adjusted 

 by the shape and size of the house and the crop to be 

 grown. The "cool" plants, like lettuce and cauliflower 

 (see page 5), do best without bottom heat, and for these 

 crops the pipes should be above the soil or bed. The 

 "warm " plants, like tomato, melon and cucumber, require 

 bottom heat, and for these the return pipes, or some of 



