THE STRUCTURE AND MANAGEMENT OF GREENHOUSES. 57 



In ornamental houses the work is done in stone and concrete 

 and with as little regularity and stiffness as possible ; a good 

 example of this sort is to be seen at the conservatory of the 

 Newton Cemetery. 



I have thus attempted to briefly describe some of the important 

 points in the structure of our greenhouses, those wonderful build- 

 ings in which the arctic blizzard is separated from the tropical 

 climate within b}' only a film of glass one-eighth of an inch in 

 thickness and where we grow the choicest productions of the 

 tropics amid the snow and ice of our truly arctic winter. 



Discussion. 



F. L. Temple said that he has a house one hundred feet long by 

 twenty wide, standing by itself, in which he has a small steam 

 boiler with an automatic draft regulator. He agreed with the 

 essayist that the econom}' of a watchman comes in in large estab- 

 lishments. The great advantage of steam is the ease and quick- 

 ness with which heat can be added or lessened ; steam pipes will 

 cool in twenty minutes. To keep up a night temperature of 40° 

 for hardy plants in such a house would require from six to ten tons 

 of coal, according to the situation and the care with which the 

 fires were managed. To keep it up to 60° would require twice as 

 much coal. He has a house two hundred feet by twenty-four, in 

 which he formerl}' used hot water, but for the last three years has 

 used steam. To keep this up to 40° in severe weather with hot 

 water took sixteen tons of coal ; with steam about twent}' tons. 



It has been objected to steam that the water must be heated to 

 212° before heat can be diffused, but there is only a little water to 

 heat, so that heat can be got up much more quickly than with hot 

 water apparatus. Some of his neighbors use hot water under 

 pressure, but he could not account for all the advantages claimed 

 for this method. It does not require so much pipe as where only 

 the pressure of gravity is relied on for circulation. Leakage is 

 more troublesome from water pipes than from steam pipes. When 

 it is desired to keep both ends of a house at the same temperature 

 it can be done better with steam than with hot water. 



William C. Strong said that the hot-water boilers heretofore 

 constructed had been imperfect, but he thought that a perfectly 

 constructed hot-water boiler would afford as equable heat as 

 steam. He had used a Gurnej' boiler with great satisfaction ; the 



