360 Proceedings of the British Association for 1850. 



acted as a shield at the mouths of the horizontal flues, and 

 prevented them from either being affected by high winds, or 

 from being choked up by materials thrown into the fur- 

 nace. The reason, no doubt, why this funnel was not 

 applied before was the great apparent temperature at the 

 tunnel-head. In practice, however, it was found that until 

 the gaseous escape mingled with the atmosphere, its heating 

 power was not such as to injure sheet-iron, or even to make 

 it red-hot. In fact, so long as there was an escape upwards, 

 the iron funnel would not be injured. The damage arose 

 during and after stoppages of the furnace, when the blast was 

 obstructed in its passage upwards by the settlement of the 

 materials in the furnace, so that the atmosphere rushed down 

 to meet the ascending gases, and, of course, caused a very 

 high local temperature. His practice was to exclude the 

 atmospheric air as much as possible. The affinity of the 

 gases for oxygen was so great that the air leakage raised the 

 temperature quite sufficient for safety, whilst the full com- 

 bustion of the gaseous escape would melt down the bricks in 

 the flues, and destroy the texture of the iron tube. It was 

 not possible for him to say what combinations took place at 

 high temperatures, where carbonic oxide, carbonic acid, hy- 

 drogen, and nitrogen, were mixed in such proportions. At 

 any rate, he found a smothered combustion to be the most 

 suitable and economical for the purposes in view. He was 

 happy to say that, at length, the application of the gaseous 

 escape had been tried in Scotland ; and that at Dundyvan 

 and elsewhere it was now in successful operation. The pe- 

 culiar quality of the furnace coal of Scotland being what was 

 called in South Wales " free burning," which, when put into 

 the furnace raw, coked sufficiently in its descent, gave out an 

 enormous escape, so much so, that, upon a rough estimate, 

 he calculated that the waste from one furnace in Scotland 

 was sufficient to heat the blast, and to raise the steam for 

 three. With anthracite coal, the minimum eff'ect was ob- 

 tained, as it was a dense fuel of nearly 95 per cent, of solid 

 carbon ; but in Scotland there would be an enormous surplus 

 at the tunnel-head. He expected, from the well-known saga- 



