MECHANICS AND USEFUL ARTS. 63 



the combined supply of air from which will be about 3,000,000 

 cubic feet per hour. One of these fans blows to the right and the 

 other to the left, the fresh air drawn from the outer atmosphere 

 being thus distributed through the chambers. This air, warmed 

 by the hot-water coils, is conveyed to the body of the hall from 

 the chamber under the main corridor by means of channels built 

 in the walls. These channels are also in communication with the 

 corridors, boxes, and all the adjoining private rooms. From the 

 chamber beneath the amphitheatre stalls the warm air finds its 

 way into the hall through perforations in the risers of the seats. 

 From the arena chamber the air enters the building through the 

 interstices between the floor-boards. By these arrangements the 

 entire power of the apparatus may be concentrated on the hall, 

 thus thoroughly warming every portion of it; at the same time 

 means are provided for warming the enclosed rooms independ- 

 ently when necessary. The amount of heating-surface in the iron 

 pipes required to carry out this arrangement is about 28,000 

 square feet. The temperature the apparatus fs calculated to 

 maintain in the hall is about 58 Fah. as a mean during the winter 

 months. 



The fresh air is supplied to the fans through 2 air-shafts, 6 feet 

 by 6 feet, which are situated at the south-eastern end of the 

 building, near the Horticultural Gardens. In each of these shafts 

 is placed a self-acting valve, fitted with an index dial which 

 registers the amount of air passing into the building. Arrange- 

 ments are also provided in these shafts for cooling the air in its 

 passage to the hall in summer by means of sprays of water. 

 The fans are 5 feet 9 inches in diameter, and are to be worked by 

 2 direct-acting engines of 3 horse-power each. The heating 

 apparatus fixed in the air-chambers consists of 16 distinct coils of 

 4-inch hot-water pipes, heated by condensing boilers so arranged 

 that each condenser has its direct coil of pipes to work. By this 

 means either a part or the whole of the coils may be utilized, 

 according to the temperature of the external air. These condens- 

 ers are supplied with steam from 2 boilers belonging to the pump- 

 ing engines of the Horticultural Gardens. In case of need a sup- 

 plementary boiler will be provided, which will give a total force 

 of about 75 horse-power. 



The modus operandi will be as follows : The temperature of 

 the hall will be raised to the requisite degree by the time the 

 audience arrives ; as soon as this point is reached, and whilst the 

 public are being admitted, the air-entrances to chambers Nos. 

 2 and 3 will be partially closed by means of valves. This 

 will allow of only one-sixth of the amount of air necessary for 

 ventilation to pass through these sources. The remaining five- 

 sixths will be distributed by means of 4 separate channels to the 

 air-chamber No. 1, under the corridor. From this chamber the 

 air will be distributed equally all through the entire building by 

 means of the air-channels formed in the walls, to which we have 

 already alluded. It will thus issue upon every floor into the body 

 of the hall, being admitted as far as possible from the audi- 

 ence. 



