GREENHOUSE CONSTRUCTION 



129 



grower. It requires less attention and is therefore desirable when a 

 night fireman is not employed. Steam is suitable for large ranges. 



Question : Do you recommend the elimination of all support as a 

 very important matter .^^ 



Professor Beal: I do not think you can eliminate the posts 

 altogether. I think with any type of construction you use there 

 comes a point in widening the house where you must use the |)osts. 

 A truss house above thirty feet in width needs some pipe supports. 



In conclusion, it may be said that the whole tendency in green- 

 house building is towards an increase in the amount of iron. In the 

 earlier forms of houses, wood was the usual material. The first step 

 in the change was the use of pipe posts in place of the ordinary wooden 

 side posts. The wooden purlins were supplanted by pipes, a pipe or 

 angle iron purlin being used for the support of the house. This addi- 

 tion of iron has brought about the semi-iron type of house. Iron 

 greenhouses have been used for a long time. Lord & Burnham built 

 the first in 1881, and they have been developing that style of con- 

 struction. At the start it was too expensive for florists to use and it 

 was employed on private places for the construction of ornamental 

 greenhouses. The rise in the price of wood has made it possible to 

 use more iron. In addition the desire for a maximum amount of 

 light has led builders to employ iron because of the greater strength. 

 The increased amount of iron used has brought the iron houses and 

 semi-iron houses and all these forms practically together, so the sig- 

 nificant fact today is that the growers are building iron houses. 



