202 STEAM.
amount of steam, which is at once disengaged. This large
quantity of suddenly formed steam forces off the upper shell
of the boiler, and causes all the mischief that follows. So
that the mischief is not done by the steam that was in the
boiler at the moment of explosion, but is done by that which
is created during the moment of explosion. This creating of
steam takes place throughout the instant of explosion, its
elastic force gradually diminishing till the water reaches
100° C. From careful investigations it may be stated
roundly, that the explosive energy in övery cubic foot of
water in a boiler at 60 lbs. pressure equals that contained in
a pound of ordinary gunpowder.
EXAMINATION QUESTIONS.
1. What are the chief causes of "boiler explosions?" What is the hydrogen theory? 2. State distinctly what you mean by the "spheroidal condition of water," and water purged from air. How have these theories been connected with boiler explosions? 3. Show how accumulated pressure and deficiency of water act to produce a boiler explosion. 4. Account for so much steam being generated and mischief done by boiler explosions. 5. What distinction is there between a boiler exploding and a tube collapsing; state the precautions to be adopted in either case.
