96 THE PRINCIPLES OF FLORICULTURE 



cult to convince many large commercial growers that it 

 would be more economical and also more beneficial to 

 plant growth to use hot-water instead of steam, in a 

 number of ranges where hot-water systems have been 

 installed, the results seem to favor that system. 



75. Controlling the heat. With either steam or hot- 

 water, it is necessary to have the heat well under control, 

 and this is possible only by the use of many valves. These 

 valves should be so placed that they can be used readily, 

 for it is often necessary to turn heat on or off at a moment's 

 notice. This is especially true on days when there are 

 frequent " sun bursts," followed by periods of cloudiness. 

 It has been asserted by advocates of steam heating that 

 hot-water cannot be so quickly and readily heated or 

 cooled as steam. To a certain extent this is true, but 

 with improved systems of water under pressure or in 

 forced circulation, smaller pipes are used, and these heat 

 or cool almost as quickly as steam pipes when the flow is 

 checked by valves. 



76. Boilers. In most modern ranges of large size 

 which are steam-heated, cast-iron, horizontal tubular 

 boilers are used (Fig. 14). They are of varying horse- 

 power, as required by the size of the range. The boilers 

 should always be large enough to furnish heat for a larger 

 glass area than is actually in use. Most large ranges 

 have the boilers arranged in batteries so that if an acci- 

 dent occurs to one boiler, it may be easily disconnected 

 and the range sufficiently heated by the other boilers. 

 Some growers prefer sectional boilers, and these are man- 

 ufactured for both steam and hot-water (Fig. 15). 

 Tubular boilers are necessarily of large size. Sectional 

 boilers are, therefore, better adapted for use on small or 

 medium-sized ranges. If additional heat is needed be- 



