356 Scientific Proceedings, Royal Dublin Society. 



unusually low down ; but nevertheless, in the construction of which 

 I have had experience, the draught, both on the lecture-table and 

 in the chamber, is excellent. The downward flues are earthenware 

 pipes 6 inches in diameter, with curved bends. 



To illustrate the efficiency of the mode of ventilating the fume- 

 chambers in the laboratory, it may be mentioned that in one of 

 them very large quantities of hydrofluoric acid were disengaged 

 at intervals during a period of nearly ten years ; and though the 

 glass of the sashes and windows was never at any time seen to be 

 attacked, the effect of it is seen at the entrance, and just within 

 the flue, by the corrosion of the slate and of the fire-bricks, more 

 particularly at the edges. The loose incrustation caused by the 

 corrosion can easily be swept away. There is an advantage in 

 sloping the bottom of the flue, as any dirt or incrustation falling 

 can be easily removed with a hand-brush. The inside of the iron 

 door to the flue should be well coated with tar, or be thickly 

 galvanized. There is at present a loose layer of rust, a quarter of 

 an inch thick, on the iron ; but this is an accumulation of fourteen 

 years. In the second of the chambers there is a considerable 

 crust of ammonium chloride on the upper surface within the 

 horizontal entrance to the flue, which, of course, is easily removable. 

 A third chamber has been used more particularly for manipula- 

 tions with sulphuretted hydrogen ; and in the flue of it there is no 

 deposit. A fourth flue is provided with an iron hood simply 

 instead of a window, under which the combustion furnace for 

 organic analysis is placed ; but there is no need to refer to this. 



With regard to the different measurements which were made, 

 it maybe remarked that the minimum amount of air which passed 

 through any one of the chambers at any season of the year and 

 under any conditions, such as dead calm or a gale of wind, high or 

 low barometer, great or little difference between inside and out- 

 side temperature, was 194*7 cubic feet per minute when there was 

 practically no gas burning ; the maximum was 421*8 cubic feet 

 per minute. The minimum was found once only out of not fewer 

 than eighty-four recorded observations ; the maximum once, also 

 out of eighty-four measurements ; but the gas consumed was at 

 the rate of 76f cubic feet per hour. The average quantity of 

 air exhausted all through was, in round numbers, 354 cubic feet 

 per minute per chamber. Sixty measurements which were made 



