WAEMING AND VENTILATION. 307 



railroad-stations, for markets, and for large buildings such as those for 

 exhibitions. 



These immense buildings, covered in most cases with glass roofs, 

 which often leave only a very small space for the escape of the smoke and 

 steam ot the locomotives and of the hot air in summer, sometimes be- 

 come unendurable for the employes. One end of the building is almost 

 entirely shut in by the gable-wall containing the main entrance; the 

 other usually has an opening only high enough for the passage of the 

 locomotive; the sides occupied on the ground-level by waiting-rooms, &c., 

 and on the second and third floors by offices, do not allow the air to 

 have access to the building, and in the hot season the temperature rises 

 near the ground-level to 104°, 113° and even 122"^, as has been observed 

 at the stations of the Lyons, Eastern, and Strasburg railroads. 



In order to remedy this state of things, it is necessary to raise the sky- 

 lights on the roof, not only because they are too low, but because in 

 winter they cool the smoke and partially condense the escape-steam of 

 the engine, and thus interfere with its removal. 



Instead of placing the sky-lights at the ridge of the roof, it would 

 seem better to place them near the eaves, making them, as at present, 

 equal to one-fourth or one-third the total surface. 



The ventilating-opening should be formed by two vertical walls of 

 sheet-iron about 10 feet high, leaving between them a passage extend- 

 ing the whole length of the roof, the breadth of which should be calcu- 

 lated so as to renew the air of the Station at least twice or three times 

 an hour, on the supposition that the heat of the sun in summer is suffi- 

 cient to produce, in a sheet-iron chimney 10 feet high, a velocity of from 

 IJ to 2 feet a second. 



To replace regularly the air removed without producing unpleasant 

 currents at the end-openings of the station, it is necessary to increase the 

 number of openings for admission of air, and place them as uniformly as 

 possible throughout the extent of the station, and also to make large 

 doorways in the two ends of the building. The total area of the fresh- 

 air openings should be such that, with a velocity of at most 16 to 20 

 inches a second, a volume of air may enter into the station equal to 

 twice or three times its cubical capacity. 



98. Sjyrinlding of roofs. — In addition to the preceding arrangements, 

 proper for all seasons, it would be well, in hot weather, to keep up a 

 constant sprinkling of the roof, commencing at seven or eight o'clock 

 in the morning and lasting till five o'clock in the evening, using about 

 44 cubic feet of water an hour to every 100 square feet of roof-surface. 



This sprinkling, which will be sufficient to prevent the heating of the 

 roof by the action of the solar rays, added to the continued aeration, 

 will maintain the temperature within convenient limits during the hot 

 season. 



99. Example. — The Orleans station is 348 feet long, 92 feet wide, 26 

 feet high at the springing-line, and 44 feet to the ridge. Its cubical con- 

 tent is about 1,130,000 cubic feet. 



