266 ON CURVILINEAR IRON ROOFS TO HOTHOUSES. 



It has been objected, that the water which drops from bars of iron is 

 extremely noxious to pine-apple plants ; but I have not found this to be 

 in any degree the case : for having placed a plant in such a situation that 

 the water from a cast-iron rafter dropped upon it, in summer, and 

 removing it only as soon as the mould became sufficiently moist, I could 

 not discover that the plant had, during a month, sustained the slightest 

 injury. Another objection made to iron roofs is, that the metal is very 

 subject to rust. This is perfectly true, provided they be not kept well 

 painted ; but if one-third of the sum requisite to keep a wooden roof 

 properly painted be expended upon the iron roof, no injury will ever be 

 sustained from the liability of that to suffer from rust. I must, however, 

 take this opportunity of observing, that the bars of all the iron roofs I 

 have yet seen have been exceedingly ill-formed. The metal, instead of 

 being rolled thin with grooves, and made to descend into the house far 

 below the level of the glass, should be compressed into the least compass 

 consistent with sufficient strength ; and its lower surface, instead of 

 being brought to a thin edge, should be hemicylindrical in form. None 

 of the edges or angles which are now presented, and which are most 

 subject to rust, would then exist ; less shade would be thrown upon the 

 plants in the mornings and evenings ; and the condensed steam would be 

 less subject to drop from the bars upon the plants ; though this, in a 

 house constructed as mine is, can never do any injury. 



I have remarked, in a former communication, that I suspected pine- 

 apple plants might suffer under the influence of a bright sun during the 

 whole length of an English summer's day, in a hot-house with a curvilinear 

 roof such as mine, if the glass were of good quality. I am not prepared 

 positively to say whether such apprehensions are well or ill-founded : 

 but I have thought it best to be provided with a net, such as those 

 usually employed to protect fruit-trees, of proper form to cover my 

 house, if necessary ; and I am satisfied that I could have used it with 

 advantage, if I had possessed it, in some very hot days in the beginning 

 of June. 



The ends of my house are of brickwork ; but I think the end opposite 

 the door ought to contain a window of about two feet square, to permit 

 a free passage of air through, upon the door being opened in very hot 

 weather : my own house is, however, without one. 



In conclusion, I wish to observe, that a curvilinear iron roof may be 

 erected at much less expense than one of wood : two shillings and six- 

 pence a foot being, I conceive, a fully remunerating price to the builder 

 of such a house as mine, the glass being white, and of the quality called 



