inch has a corresponding
opposite square inch, and the seam of shell must sustain this pressure,
and as a single riveted boiler only affords 62 per cent of the strength
of solid iron. It is something that every engineer ought to consider.
He ought to be able to thoroughly appreciate this almost inconceivable
pressure. How many engineers are today running 18 and 20 horse power
engines that realizes that a boiler of this diameter is not capable of
sustaining the pressure he had been accustomed to carry in his little 26
or 30 inch boiler? On page 114 You will get some idea of the difference
in safe working pressure of boilers, of different diameters. On the
other hand this is not intended to make you timid or afraid of your
engine, as there is nothing to be afraid of if you realize what you are
handling, and try to comprehend the fact that your steam gauge
represents less than one 1-1000 part of the power you have under your
management. You never had this put to you in this light before, did
you?

If you thoroughly appreciate this fact and will try to comprehend this
power confined in your boiler by noting the pressure, or power exerted
by your cylinder through the small supply pipe, you will soon be an
engineer who will only carry a safe and economical pressure, and if
there comes a time when it is necessary to carry a higher pressure, you
will be an engineer who will set the pop back again, when or as soon as
this extra pressure is not necessary.

If I can get you to comprehend this power proposition no student of
"Rough and Tumble Engineering" will ever blow up a boiler.

When I started out to talk engine to you I stated plainly that this book
would not be filled up with scientific theories, that while they were
very nice they would do no good in this work. Now I am aware that I
could have made a book four times as large as this and if I had, it
would not be as valuable to the beginner as it is now.

From the fact that there is not a problem or a question contained in it
that any one who has a common school education can not solve or answer
without referring to any textbooks The very best engineer in the country
need not know any more than he will find in these pages. Yet I don't
advise you to stop here, go to the top if you have the time and
opportunity. Should I have taken up each step theoretically and given
forms, tables, rules and demonstrations, the young engineer would have
become discouraged and would