130 HORTICULTURAL STRUCTURES. 



moreover one of a most inviting character. One great fact 

 should be hud in view, in approaching this question ; the fact 

 that most of the injuries from intense sunlight occur from about 

 eleven a.m. to two p.m. 



Now span roofs, or any multiple of them ; call them ridge and 

 furrow or what we will, if running north and south, and conse- 

 quently presenting morning and evening slopes, are just calcu- 

 lated to avert that evil ; and not only that, but to present such 

 advantages as at once to carry weight, whatever defects they may 

 have. I have certainly known this burning, blistei'ing, &c., occur 

 at four or five in the afternoon, but then it has invariably been 

 through bad management : the person in charge of the houses 

 has closed them injudiciously, or your "stoke-hole-man'' has 

 been wasting his fuel. 



It is really lamentable to see (as is no very uncommon thing 

 with metallic structures) the gardener driven to shading, and not 

 only that, but prevented closing his house, or at least reducing 

 his air betimes in the afternoon, through dread of this scorching. 

 And yet, such is at times the case, and thus that great maxim 

 with the forcing gardeners of shutting in much solar lieat betimes, 

 both on principle and economy, is set at nought, and after perhaps 

 extreme aridity with a shifting air, he is obliged to betake himself 

 to extra fire heat in order to make sufficient progress ; it is surely 

 almost needless to say how much inferior in principle, as well as 

 more costly, is the latter proceeding. 



The great accumulation of heat, too, at the upper portion of 

 the roof; how unnatural, how wasteful ! It is scarcely too much 

 to affirm that ten per cent of the fuel is wasted in this angle, 

 especially in high houses with a smart incline. And then the old 

 sliding upper sashes to let this unnecessary accumulation escape ; 

 how liable to cause expense ! But, in a ridge and furrow running 

 north and south, it may be presumed that in ordinary cases bold 

 pediment ends, capable of being thrown open, together with ample 

 provision at low levels for the ingress of fresh air, will generally 

 suffice. I have, during the last four or five years, made a point 

 of talking this subject over with really experienced gardeners, 

 when I could fall in with them, and of inviting them to urge as 

 many real difiiculties as they could in the way of the north and 

 south span roof ; but I have never been able to collect opposing 

 evidence worthy of grave consideration. 



I therefore respectfully submit the question to tlie consideration 

 of the readers of the Horticultural Societv's Journal, and should 



