not attending to it may often be seen in buildings, sucli as 

 churches, where there is a succession of galleries, the whole 

 floors usually forming series of natural gratings, and the descent 

 and ascent of cool and heated air going on continuously : but 

 from the absence of some contrivance to secure the application of 

 the atmospheric air to the hot-water j)ipes, the cool air descends 

 only to the first series of pipes, and an immense waste of power 

 is of course the result. The system of heating the Houses of 

 Parhament was found defective from this circumstance, the cool 

 air being brought at once from the outside instead of from 

 another part of the buildings ; hence the succession of hot and 

 cold draughts, which were found so unbearable in winter and so 

 disagreeable at all seasons. In the system at present adopted by 

 the Eoyal Horticultural Society, provision is made not only for 

 heating, but also for circulating the atmospheric air throughout 

 the building, and conducting it beneath the hot-water pipes. 



Channels for the introduction of cold air from the exterior 

 of the building, when necessary, are also provided; but these 

 channels are fitted with registered ventilators, so as to allow 

 the supply of fresh air to be regulated, and to admit only a 

 limited supply during inclement weather, as well as to prevent 

 draughts. 



The hot-water apparatus erected in the Conservatory is in- 

 tended to accompHsh a twofold object, namely, to warm the 

 building efficiently, and to promote a thorough and satisfactory 

 ventilation. 



By means of boilers, circulating castings, ventilating grates, 

 air-passages, and valves, the heating and ventilating are made 

 in a great measure self-acting. 



