'♦'♦ii 



The boilers are of upright tubular construction, and connected 

 with similar hollow furnace-bars, through which the whole of the 

 water passes previous to entering the boiler. The water is thus 

 made to pass beneath the fire, and so to secure the benefit of 

 that heat which ordinarily descends into the ash-pit and is 

 wasted. Each of these boilers contains 76 tubes, and exposes a 

 heating surface of about 400 superficial feet to the immediate 

 action of the fire ; hence, by applying a simple formula (one foot 

 of boiler surface acted on by the fire being capable of heating 

 about 35 feet of 4-in. pipe) we find that each of these boilers is 

 capable of heating not loss than 14,000 feet. 



The boilers, placed in their respective positions, are connected 

 at the top by circulating castings. These castings are fitted with 

 two metal valves, 6 inches in diameter ; so that by the regulation 

 of the valves the water can be shut oS from one boiler while the 

 other is worliing the apparatus, as, for instance, during repairs 

 or other alterations. Nor is this the only precaution adopted : 

 two separate mains, of large diameter, are brought from the 

 boilers into the Conservatory. These also are each fitted with 

 additional valves, in order to render the whole doubly secure. 

 Thus, if any portion of the apparatus were to become dis- 

 arranged, half the quantity only of the pipes might be heated, 

 and half the water witlidrawn. 



The galleries of the Conservatory are heated on a somewhat 

 difierent principle. Here there were no means of placing pipes 

 below the floor, and an unsightly barrier of pipes four deep, 

 one above the other, running round the gallery, is avoided by 

 adopting tubular coils, which are treated as pedestals, and used 

 as stands for ornamental objects. A small boiler of similar con- 



