352 Scientific Proceedings, Royal Dublin Society. 



A further necessary provision is that the external opening of 

 the flue should be carried above the pitch of the roof ; for other- 

 wise sudden and powerful blasts of wind descend, the effects of 

 which are fraught with danger to those using the chambers, both 

 from poisonous gases and from explosions. Explosions are liable 

 to occur when the reversed draught extinguishes the gas-jet under 

 the flue, and fills the chamber with an explosive mixture of gas 

 and air which may be easily ignited by the flame of a burner on 

 the floor of the chamber. A serious explosion of this kind has 

 been known to occur. 



I propose to give a description of the most efficient and simple 

 mode of ventilating draught-chamber I have yet seen, with a series 

 of measurements made daily during a period of five weeks, both 

 of the air extracted and the gas burned. Observations were 

 actually conducted over a period of six months. The actual 

 successful working of these chambers has continued uninter- 

 ruptedly for fourteen years. (See Plate XXXIII.) 



Each fume-chamber inside is 4 ft. 10 in. broad, 2 ft. 6 in. 

 deep from front to back, and 4 ft. 3 in. high ; the slope of the 

 roof is 6 inches. The floor of the chamber is sunk 3 in. below 

 the framework, and is covered with lead overlying a slate bed. 

 Outside the chamber, and at the right-hand side, is the tap for 

 water-supply, the spout of which is 27 in. above the floor of the 

 chamber and inside it ; the service being at high pressure, and 

 the delivery a half-inch pipe, the chamber can be flooded almost 

 instantly ; for all that, when not otherwise required, the water- 

 supply can be used for cooling condensers, filling water-baths, &c. 

 At the left-hand corner is the out-flow for waste water. The 

 acid from a large Kipp's sulphuretted-hydrogen apparatus can be 

 discharged into this without any trace of the gas escaping into 

 the laboratory. At the right-hand side, the flue of 9 in. square 

 section is built into the wall, and terminates above the pitch of the 

 roof. At 12 in. above the floor of the chamber, an opening 9 in. 

 square passes horizontally to the bottom of the flue. The bottom 

 of the flue is a small chamber 13 in. wide, and 16 in. from front 

 to back, larger, therefore, than the flue itself ; and the floor of this 

 rises from the horizontal opening, the slope being about 30°. In 

 the wall of the room, about 3 ft. above the bottom of the chamber, 

 is an iron door about 18 in. square, 17 in. broad, by 16 in. high. 



