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, . 
