WARMING AND VENTILATION. 321 



but on account of the ornaments which break up the passage it will be 

 necessary to make them 10 inches either in height or in developed profile. 



These arrangements will insure the renewal of 954,000 cubic feet of 

 air an hour, or 1,590 cubic feet to each person, if there are 000 present^ 

 suflBcient in all seasons to secure the healthful condition of the room 

 and to moderate its temperature ; but it is not necessai-y that they be 

 isolated and confined to one of the reception rooms of the palace. It 

 ■will be equally necessary to adopt similar arrangements for the two 

 adjoining rooms, which often contain many persons, and also for the large 

 gallery, frequently used as a ball room. It may not be unnecessary to 

 add that for evening parties the two large fire-places which are in the 

 grand gallery may, by means of gas-burners placed within them, serve 

 as ventilating-chimneys ; and if there is any difficulty in cutting in the 

 side- walls descending flues leading to the basement, ascending flues may 

 be made, separate, or communicating with a single ventilator placed in 

 the roof over each room. 



The fresh air should enter above the cornice, and in a horizontal direc- 

 tion. 



Each of the principal saloons in the palace should thus have its own 

 ventilators provided with regulating-valves ; they should be independent 

 of the others, and this will prevent the unpleasant currents which would 

 otherwise arise as the guests take their departure. 



HALLS OF ASSEMBLY AND LECTURE-ROOMS. 



120. These places of temporary resort, where there is often more than 

 one person to every square foot of floor-surface, should be ventilated 

 at the rate of 1,000 cubic feet of air an hour to each person. 



The arrangements which I have adopted for the main lecture-hall of 

 the Conservatory of Arts and Trades, and of which the satisfactory re- 

 sults have been seen every day for five years, appear to me worthy of 

 imitation. 



The foul air is drawn off through openings in the risers behind the 

 feet of the auditors, and their total clear area for the passage of the air 

 — deduction being made for the solid portions of the grating, if there 

 are any — should be calculated so that the air will only attain a velocity 

 of 28 or 30 inches a second. This surface also should be distributed as 

 uniformly as possible among the steps. 



The basement under the lecture-room, kept as clear as possible, should 

 communicate with a ventilatiug-gallery, placed underground or at the 

 -ground-floor level if possible, the sectional area of which should be 

 calculated so that the velocity of the air shall not be greater than 4 

 feet a second. 



This gallery should terminate in a ventilating-chimney, the mean sec- 

 tion of which should be determined on the condition that the velocity 

 of the air shall reach 5 or 7 feet a second in order to secure the perma- 

 nence of the current. 

 21 s 



