AMERICAN ASSOCIATION OF NURSERYMEN. 307 



the roots ami in the plant to keep it well if there is no draft of air allowed 

 to circulate through them. 



President Sweet : We will open the afternoon session liy a paper from 

 our old-time friend, Peter Henderson of New York, on the best method of 

 preserving- wood in greenhouses, and with reference to the best method of 

 heating. 



In considering the best method of preserving wood in greenhouses, the construction 

 and painting must be taken into consideration. There must be no joints or open spaces 

 between the different sections where water can get into the wood. Such joints as can 

 not be avoided in the construction should be made very close and put together with 

 white lead. No sap or shaky hunber should ever be used. To best preserve the wood in 

 painting, the first coat should be raw linseed oil with very little lead in it, and all sub- 

 sequent coats should be mixed quite thin. There is probably no substitute equal to 

 white lead and oil for this work, and it is the oil which is of chief value in the preservation 

 of the wood; when the oil is exhausted, the remaining lead is of no further value as a 

 preservative. New wood absorbs the oil largely the first year, so that it is imjjortant 

 and economical to repaint a house after the first twelve months; if this is properly done 

 the painting will stand good for several years. I would advise, for commercial work, 

 painting two coats when the work is put up and a third coat, mostly oil, after twelve 

 months. For the benches of greenhouses, yellow or Georgia pine is preferable to 

 either spruce or hemlock. 



HEATINCi GREENHOUSES — HOT WATER OR STEAM. 



There is almost an equal division of opmion on this subject. In our judgment, when 

 the range of glass is sufficient to employ a night watchman, say 50,000 square feet, steam 

 has several advantages over hot water, chief of which are: The exact regulation of tem- 

 perature, which can be obtained by close attention, and consequent economy of fuel, 

 and the convenience of placing the heating furnaces all at one point. For example, we 

 have a range of glass where the extreme point is about 600 feet away from the boilers ; 

 it would hardly be practicable to heat by hot water at that distance, but for all medium 

 and small-size greenhouse establishments, whether for commercial or private purposes, 

 we recommend the use of hot water. The regulation is simple. The size of the green- 

 house or greenhouses to be heated must determme the capacity of the boiler wanted : 

 but the boiler being properly apportioned to the length of pipe, the following data, used 

 in our own establishment, niay be useful. In our houses, which are twenty feet wide 

 and 100 feet long, when a night temperature of 70 degrees is required in the coldest 

 weather, ten runs or rows of four-inch pipe, five on each side, are used; when 60 degrees 

 are wanted, eight runs of pipe, four on each side, when 50 degrees are wanted, six runs 

 of pipe; and when onlv 35 or 40 degrees are wanted, four runs of pipe. This is for the 

 latitude of New York City, where the temperature rarely falls lower than 10 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 10 degrees 

 below zero, to keep a temperature of 50 degrees in the greenhouse. A one-and-a-quarter- 

 inch pipe, when heated by steam, does almost exactly the same amount of heating as a 

 four-inch pipe heated by hot water. 



ARE IRON GREENHOUSES A SUCCESS ? 



Whether iron greenhouses are a success or not depends on permanence of construc- 

 tion, relative cost, and economical heating ; and on the average advantage or disadvan- 

 tage shown bv the answers to these questions would depend the answer, yes, or no, to 

 the main querv. Iron has been used for skylight and depot roofs for several years, and 

 for these purposes is considered a success, but the conditions in greenhouse building 

 are very different. Construction of common greenhouses of iron without the use of more 

 or less wood has not been attended with such a degree of success as to warrant its com- 

 mendation. T\ r^ 



In the original construction of the botanic garden conservatories, \\ ashiugton, D. C, 

 iron was used exclusivelv for the roof, but owing to the expansion and contraction of 

 the metal, and consequent loosening of and l)reakage of the glass, after various costly 

 exijeriments with ditferent forms of metal construction, light wood caps for all the iron 

 parts were provided, and with this modification, the houses have stood for many years, 

 and are verv satisfactory. Where metal is used exclusively, the expansion and contrac- 

 tion caused' bv the extreme changes of our climate are so great that it has been found 



