112 THE PRINCIPLES OF FLORICULTURE 



are numerous coils of all lengths, sizes and shapes con- 

 forming to the peculiarities of the range of houses and to 

 the bench arrangement in the houses. The expansion 

 tank is not in the attic on the second, third or fourth 

 floor, as in dwelling house work. It is often, in fact, 

 within 4 feet above the level of the coils, so there 

 is very little head, and the circulation due to gravity 

 alone is in some coils sluggish, to say the least, in large 

 ranges. To such systems a circulator or accelerator is a 

 decided benefit. 



" In other cases a small centrifugal pump is used. This 

 pump may be driven by an oil engine, a gas engine, a 

 steam engine or by electricity. In still other cases a 

 large steam boiler or battery of boilers is used, and the 

 water is heated in a large converter or feed water heater, 

 the water being heated by live steam from the boilers, 

 the circulation forced by a large, steam-driven centrifugal 

 pump, rotary pump or double-acting piston pump, and 

 perhaps a secondary or exhaust steam heater is used, 

 through the coils of which exhaust steam is passed, so 

 getting as fine an economy as possible. 



" Pea-coal, buckwheat, rice-coal, screenings, or slack, 

 the cheapest fuel procurable, is burned by means of a 

 fan or forced draft. In still other cases the water is 

 heated in a large tubular boiler. A smaller steam boiler 

 furnishes the power for driving a small engine required 

 for the operation of the fan and pumps, and the surplus 

 live steam from the steam boiler may be used for auxiliary 

 steam radiation for evaporating sulfur in the houses, for 

 keeping gutters free from ice, or for heating manure water 

 and very little heat need be wasted. 



" The mains for such a system are small. They are 

 smaller than are necessary for the steam main of a steam 



