MECHANICS AND USEFUL ARTS. 25 



BOILER EXPLOSIONS AND THEIR CAUSES. 



The subject of boiler explosions has been discussed at great length 

 during the past year in English scientific periodicals. In the London 

 Engineer and London Mechanics' Magazine, editorial articles and 

 contributions from correspondents have appeared weekly, in which 

 various theories have been advanced, attacked, and defended ; and 

 the conflict still goes on. The discussion has excited our attention 

 not only on account of its nature, but also because of the persons who 

 have ta'ken part in it, such as C. Wye Williams, the author of a valu- 

 able work on combustion; D.,K. Clark, author of the incomparable 

 work on locomotive engineering, and Zerah Colburn (now in Lon- 

 don), an able American writer on railway engineering topics. Quite 

 a number of others, whose names we omit, have also taken part in 

 the discussion. There is still some apparent mystery connected with 

 the phenomena of boiler explosions, or we would not have so many no- 

 tions and theories floating about respecting their causes. The most 

 common theory of boiler explosions is that of accumulated over-pres- 

 sure of steam generated by the heat in the furnace. This theory em- 

 braces defects in the boiler, also the absence of a sufficient quantity of 

 water, whereby the metal is permitted to become red hot and weak, 

 and is capable of explaining most of the explosions which have oc- 

 curred. 



The theory of C. W. Williams is to the effect that steam is concen- 

 trated in the water under pressure in a steam boiler, like carbonic 

 acid gas in soda water, and when it is relieved of pressure it suddenly 

 assumes a violent expansive action. 



The theory of D. K. Clark consists in considering the water in the 

 boiler necessary to produce an explosion, by acting like a projectile 

 with a bounding force against the metal. 



Mr. Zerah Colburn's hypothesis consists in assuming that when wa- 

 ter, heated with steam above atmospheric pressure, is suddenly re- 

 lieved of pressure by a large rupture, a considerable amount of the 

 water is instantly flashed, gunpowder-like, into steam. Scientific 

 American. 



NOVEL ARRANGEMENT OF STEA1I BOILERS. 



At the meeting of the Society of Civil Engineers of Vienna, Aus- 

 tria, M. Strecker communicated a very ingenious and simple mode of 

 preventing the burning of steam boilers. This apparatus, invented 

 by M. J. Haswell, director of the Vienna Locomotive Factory, con- 

 sists in introducing into the interior of the boiler a small turbine, 

 which continually drives the water from the bottom towards the front 

 of the boiler ; thus on the one hand cooling the walls which are most 

 liable to overheat, and on the other facilitating the formation of 

 steam. 



WORKING STEAM EXPANSIVELY. 



During the winter of 1860-61, experiments were made, under 

 order of the Secretary of the Navy, by a Board of Chief Engineers 

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