HEATING BY STEAM. 101 



required, four runs of pipe will meet the requirement. 

 This is for the latitude of New York City, where the 

 temperature rarely falls lower than ten degrees below zero. 

 Latitudes north or south of New York should be graded 

 accordingly.. If estimated by glass surface, about one 

 foot in length of four-inch pipe is necessary for every 

 three and a half square feet of glass surface, when the 

 temperature is at ten degrees below zero, to keep a tem- 

 perature of 50 degrees in the greenhouse. We now place 

 all our pipes under the side benches, as that enables us to 

 use the space under the middle bench for safely stowing 

 away many plants, which otherwise could not be done if 

 the pipes were there. There are scores of kinds of hot 

 water boilers in use, and our opinion is repeatedly asked 

 as to the relative merits of many of them. This can only 

 be determined by a comparative test, which we have 

 never had time or inclination to try. We have used the 

 boilers made by Hitchings & Co. for the past twenty 

 years with the most satisfactory results. There may be 

 better, but we do not know them, and do not care to take 

 the risk of experimenting. 



CHAPTER XX. 

 HEATING BY STEAM. 



Two years ago, to satisfy myself of the relative merits 

 of hot water and steam heating for greenhouse purposes, 

 I erected a Rose house twenty feet wide by 350 feet in 

 length. This I heated by steam alongside of another 

 Rose house of exactly the same dimensions, heated by hot 

 water. These have given me an opportunity for a com- 

 parative test and we find the result in favor of steam ; 



