Notes on Steam Boilers. 321 
preventing explosions ; and not only is this the best 
guarantee of safety, but also a great source of economy, 
through the dete6fcion of slight flaws, which, if allowed to 
continue, develop into serious defe6ls, requiring expen- 
sive repairs, besides causing serious corrosion to other 
parts through leakages. There can be no doubt that a 
great number of accidents are stri6lly preventible, while 
others are nothing of the kind ; and it is to the former that 
we must dire6l our attention, since no amount of examina- 
tion could deteft hidden or buried flaws. A steam boiler 
can be made when new to resist a given pressure say 
ioolbs. on the square inch, and its power of doing mischief 
is so far limited. When that boiler is at work, there are so 
many thousand foot tons of energy locked up in it, which, 
if the shell plates or flues give way, will be let loose in 
a moment to do fearful damage. The strength of the 
boiler plates is the agency by which we control the force 
of the steam. If the plates are allowed to become too 
weak by corrosion, there is an explosion, but this explo- 
sion is seldom an accident, but the result of negligence, 
ignorance or parsimony. One of the first to take up the 
matter of boiler explosions, and seriously consider them, 
was the late Sir WILLIAM FAIRBAIRN, who in 1 854, founded 
the " Manchester Steam Users Association, " for the pre- 
vention of steam boiler explosions, and lor increasing the 
efficient working of steam engines ; and since then much 
good work has been done. However, much remains for 
us Mechanical Engineers to accomplish, especially when 
we remember that in our most efficient arrangements for 
obtaining work out of coal, over 80 percent, of the heat 
is wasted. 
A Steam Boiler is simply a thing to absorb heat. 
