Gkeenhouse Notes. 163 



The piping was all designed for hot water; that is, the highest 

 points in the risers or flows were at the further extremities of the 

 runs. All the conditions, therefore, were decidedly in favor of hot 

 water; and whatever advantage steam may have had in our first 

 experiment, it was much overbalanced in the present investigation. 

 This little heater was used to warm a small cool house, used for let- 

 tuce and other plants requiring similar temperature, and comprising a 

 ground area of 432 square feet. It is a lean-to house, facing the south, 

 with the back wall 9 feet high. Thermometers were let into the pipes 

 for the purpose of obtaining inside temperatures, after the manner 

 explained in Bulletin 41. These experiments were conducted by 

 Fred W. Card, Fellow in Horticulture, who made the former investi- 

 gation, and the remainder of this paper comprises his accounts of the 

 subject. 



Methods. — The experiments of the present season were made in a 

 lettuce house about 16x27 feet in size, with ground beds and a 

 lean-to roof. It is protected on the west, north and east sides 

 by the general work-room; a solid wall of earth, and a cool pit 

 respectively, leaving only the south side and roof exposed, both 

 of which are covered with third quality single-thick glass. The 

 same boiler and the same piping served for all tests except the last 

 one of both steam and hot water, when a long run was added, to test . 

 the results of a more extended circulation. The only change ever 

 made in the apparatus was the removal of the expansion tank when 

 steam was used. This tank was placed near the roof of the work- 

 room and was about 9 feet above the top of the boiler. The level of 



7. When the fires are operative, the fluctuation in the temperature of the 

 risers at any given point is much greater with hot water than with steam. 



8. An increase in steam pressure raises the temperature of the entire cir- 

 cuit, but the temperature does not rise uniformly with the pressure. 



9. The first appUoation of the pressure increases the temperature of the 

 returns much more than that of the risers. 



10. Steam is better than hot water for long and crooked circuits. 



11. Pressure is of great utility in increasing the rapidity of circulation of 

 steam, and in forcing it through long circviits and over obstacles. 



12. Unfavorable conditions can be more readily overcome with steam than 

 with hot water. 



13. Hot water consumed more coal than steam; and was at the same time 

 less efficient. This result would probably be modified in a shorter and 

 straighter circuit, with greater fall, 



14. Under the conditions here present, steam is more economical than hot 

 water and more satisfactory in every way ; and this result is not modified to 

 any extent by the style of heaters used. 



