Hartley — On the Construction of Fume- Chambers. 355 



door as a powerful draught. Measurements were made of the air 

 which thus passed into the building ; and it was found to be 

 63,000 cubic feet per hour, or, more precisely, 1054 cubic feet per 

 minute. This is nearly identical in quantity with that which 

 went up the flues. 



The following are particulars of an average set of measure- 

 ments taken at the door: — 



Over 5 feet 1 inch from the floor there was no steady inward 

 current, but occasional gusts of wind rushed in. 



Rate of Floiv of Air-currents. 



At the left-hand side of Midway on a horizontal line At the right-hand side of 

 doorway. 5 ft. 1 in. ahove the floor. doorway. 



100 ft. per minute ... 123 ft. per minute ... 44 ft. per minute. 



At 4 feet ahove the floor. At 4 feet above the floor. At 4 feet above the floor. 



126 ft. per minute ... 157 ft. per minute ... 63 ft. per minute. 



At bottom. At bottom over floor-level. At bottom. 



127 ft. per minute ... 144 ft. per minute ... 170 ft. per minute. 



At a height of 5 feet from the floor, on the right-hand side, 

 the flow was irregular ; sometimes there was no inward current. 



So far the description applies to vertical flues; but the same 

 arrangement of a vertical flue connected with a down-draught has 

 been applied to a lecture-room table, and at the same time to an 

 adjacent draught-chamber ; the current of air in these cases flows 

 first downwards, and then is discharged vertically upwards. It 

 is essential for efficiency that this discharge be vertical ; and, for 

 securing this condition, an old flue in the wall of the room was 

 slightly diverted at its lower end from its original direction, which 

 was crooked. 



One point of importance to be attended to in lecture-room 

 ventilation is, that the two flues which pass downwards, one from 

 the lecture -table and the other from the draught-chamber, should 

 not differ greatly in vertical height from the floor ; otherwise the 

 draught in one will be greater than that in the other. On this 

 account they should be made to open at or about the same level. 

 This makes the position of the opening in the fume-chamber 



