THE FLORAL WORLD AND GARDEN GUIDE. 345 



House will be preferable. It is cheap to construct, not difficult to 

 manage, and economical in working. 



In a few weeks from the time of this appearing in print, we may 

 expect rather sharp frosts, and those who have work of this kind on 

 hand, should push it on rapidly, so as to avoid being caught, and 

 losing a portion of their stock, because of the apparatus not being 

 in working order. So far as regards heating horticultural struc- 

 tures with hot water, it appears to me that there is yet much 

 to be learnt. Many persons build houses, and set boilers, and furnish 

 them with just one certain amount of hot-water pipes, without any 

 consideration as to whether a proper amount of heating surface 

 has been given to secure the success of the undertaking. I have 

 seen many useful and handsome buildings erected, and a powerl'ul 

 and expensive boiler attached, and those most interested in it 

 showing the utmost anxiety that these two essentials should be 

 perfect. But when coming to the question of hot-water pipes, it has 

 been dealt with in a niggardly manner. There is a very simple 

 means of ascertaining by calculation the amount of piping required 

 to heat a given space of air, and this is often done to know the 

 required quantity for any one house, and on the strength of such 

 calculations inexperienced people act, and then comfort their minds 

 in thinking that they have done all that means and skill could do — 

 in fact, all that is wanted to be done to make their investments 

 a perfect success. But such calculations are faulty ; they cannot 

 be said to be erroneous. They are faulty because tliey make the 

 basis of their calculations an imaginary condition of the elements, 

 not reckoning for external influences. Therefore it is that they are 

 not applicable to the ordinary structures used as horticultural 

 buildings, unless they make their calculations, which is seldom or 

 ever done, from two extreme points. Por instance, if we take a 

 certain house in which the temperature ranges regularly at 40"", we 

 can easily ascertain by calculation how much piping it would require 

 to raise the temperature to 60°, and secure at the same time that 

 there be sufficient surface, that the heat generated from the pipes 

 shall not be of that parching character wnich results from pipes 

 excessively heated, as they must be where there is insufficient 

 surface. But then such calculations do not go far enough ; they 

 only proceed, Ave may safely say, to one extreme point; for a house 

 that is maintained at 40° without artificial heat, must be favoured by 

 an external atmos^phere never lower than 35'^. Therefore, when we 

 wish to raise this liouse, by the application of artificial heat, to 60°, 

 we cannot expect that the same amount of heating surface that 

 serves when the tliermometer reads 35", will serve equally well when 

 it is 20" lower. Nevertheless, many houses are heated in a way 

 which compels us to suppose that the authors of the heating appa- 

 ratus believed this to be possible, for there is no extra amount of 

 piping sufficient to make up the required degree of heating surface 

 when the external influences should demand it. 



JS'ow as a consequence of this deficiency of heating surface, we 

 are obliged to heat to such a pitch the few pipes that we have, that 

 the heat given oS from them is so great that it is positively injurious 



UoTember. 



