42 THE CONSTRUCTION OF THE FORCING-HOUSE. 



obstacles, as elbows and angles and obstructions, better than 

 hot water. It travels faster and farther. Crooked runs with 

 little fall are great difficulties in hot water heating. Steam 

 can be varied more quickly than hot water. On the other 

 hand, steam is as steady as hot water under proper manage- 

 ment, and it requires but little more attention. Practically 

 the same treatment is required by both water and steam 

 heaters. Plants thrive as well under steam heat as under 

 hot water heat. The opinion that steam heat is a "dry 

 heat" is erroneous. Hot water heating demands from a half 

 to twice more piping than steam heating, and the original 

 cost is, therefore, greater. This additional piping has a cer- 

 tain advantage, however, inasmuch as each pipe is less hot 

 than in steam systems and is less likely to injure plants 

 which stand close to it. This advantage is not great, how- 

 ever, especially in forcing establishments, where no injury 

 need ever come from hot steam pipes. There is no uniform 

 advantage in consumption of fuel in either system. Theo- 

 retically, hot water is probably more economical than steam, 

 but in practice the cost is determined largely by the particu- 

 lar pattern of heater and the general efficiency of the sys- 

 tem. Some tests show water to be the more economical, 

 and other tests give the advantage to steam. In other 

 words, the fuel consumption is largely a local question. 



The summary results of various experiments upon the 

 comparative merits of steam and water for heating plant 

 houses, made at Cornell University (and reported in Bulle- 

 tins 41, 55 and 96), are as follows : * 



1. The temperatures of steam pipes average higher than 

 those of hot water pipes, under common conditions. 



2. When the risers or flow pipes are overhead, the steam 

 spends relatively more of its heat in the returns, as bottom 

 heat, than the water does. 



* Other studies in glass house heating will be found in Bulletins 4, 6, 8 

 and 15 of the Massachusetts Hatch Station (by S. T. Maynard), and in 

 Bulletin 63 of the Michigan Station (by L. R. Taft). In these experi- 

 ments, water gave the better results. 



