336 History of Mechanical Inventions and 



from one of the boilers exploding a little while before the other. In this case 

 it seemed clear after the accident, that the steam had not acquired any formi- 

 dable degree of pressure, and that the water had not been so low as to en- 

 danger the tube being improperly heated. One man was killed, and the in- 

 terior tubes of the boilers were much contorted and rent. The third explo- 

 sion took place at East Crennis mine. The inner tube was compressed as 

 if the fire had softened the part above it, though there did not appear to be 

 any other reason to think that the water was too low. The ends were torn 

 to pieces, and the tube was thrown out of the outer tube and out of the boiler, 

 while the inner tribe remained in its place, and was scarcely injured. No per- 

 son was materially injured. The last accident happened in the Pen-y-fron 

 Engine, at the Mold mines in Flintshire, to a boiler of a similar construc- 

 tion. The outer tube remained in its seat uninjured, and even the weight 

 on the lever of the safety valves was not disturbed. The inner tube was 

 not moved from its place, but was flattened for a great part of its length, 

 the ends having been squeezed together, and not the top and bottom, as at 

 East Crennis. It seemed certain that the pressure of the steam did not ex- 

 ceed 30lbs an inch, and that the water was at its proper height. When the 

 engine-man had put down the damper in the flue, he observed a gust of 

 flame rushing from the fire place, and almost immediately after an explo- 

 sion. This made him jump from a door very considerably above the level 

 of the ground below, as the engine stands on the side of a steep hill. He 

 alighted on the heap of ashes which were always discharged at the door, 

 and got out of the way before the hot water rushed out. Other two men in 

 the boiler house were killed instantly by the boiling water, no other injury 

 being observed on their bodies. 



Prom this case Mr Taylor is led, very ingeniously, to ascribe the bursting 

 of the boiler to an explosion of an explosive mixture of coal gas and atmo- 

 spheric air. When the fire door was thrown open, and the current of air up 

 the flue stopped by closing the damper, the interior of the inner tube con- 

 tains a mixture of coal gas and atmospheric air. The coal gas is increased 

 by the distillatory action of the fire, until the mixture reaches the explosive 

 point. It then takes fire, occasions the observed rush of flame, which 

 would be followed by a sudden vacuum in the tube, while the other side of 

 the tube, pressed by the steam, gives way to this sudden impulse. 



In support of this opinion, Mr Taylor adds, that bursts of flame are 

 often observed from the chimneys of steam-engines illuminating the sur- 

 rounding scene. These bursts of flame often rise above the summit of the 

 stalk, and are seen to emerge, diminishing and retiring into the flue after 

 a blaze of some minutes, and leaving all in perfect darkness. 



It is generally supposed that high-pressure boilers are most liable to 

 accidents, but this is not the case. About twelve months ago, a boiler of 

 the old spherical construction burst at a mine in Flintshire, about seven 

 miles from the Mold mines, and occasioned the death of sixteen persons. 



5. Account of a New Method of Bleaching and Preparing Flax and 



Tow. By the Rev. T. B. Emmett. 

 This process, which is said to be simple, easy, and cheap, and to reduce 

 the material to a beautiful degree of whiteness, is as follows: 



