VENTILATION AND VENTILATORS. 
413 
through the open window, and unless this be supplemented by 
an artificial contrivance, we know of no other better method. At 
night, the employment of gas, with a central air-shaft, is likely to 
produce a tolerably good in-draught by removing the foul air. 
The chimney, too, is thought to assist in producing a current 
outwards, but this does not always happen ; indeed, it not un- 
frequently occurs that the draught through the chimney is into, 
not out of, the room. A convenient mode of remedying this, 
but one which is seldom used, is to keep a small gas-jet burning 
