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 never have read it through.  He would have become discouraged because he could not understand it.  Now to illustrate what I mean, we will go a little deeper and then still deeper, and you will begin to appreciate the simple way of putting the things which you as a plain engineer are interested in.

For example on page 114 we talked about the safe working pressure of different sized boilers.  It was most likely natural for you to say “How do I find the safe working pressure?” Well, to find the safe working pressure of a boiler it is first necessary to find the total pressure necessary to burst the boiler.  It requires about twice as much pressure to tear the ends out of a boiler as it does to burst the shell, and as the weakest point is the basis for determining the safe pressure, we will make use of the shell only.