But engineers often err in presuming that "side issues" have no place in their calculations. It is one of the most common mistakes, leading to the charge of impracticality. We strip our data down to the necessary and sufficient considerations, and try to forget that nature doesn't often present the problem in that way. She is very likely to clutter up the job she assigns us with a wholesale lot of unnecessary facts, more or less related to the main issue, and then, away off in the dim and dusky corner, hide one of the vital bits of information without which we cannot hope to solve her puzzle. She loves to impose upon our doings a heterogeneous bunch of conditions, limitations or even obstructions—impedimenta, so to speak —baggage to be carried along on the journey, not all of which may be useful.
Many processes require the presence of operators whose elimination, in later stages, is necessary, before the completion of the work. For example, a recent bulletin coming to my desk shows that each pound of paper produced from wood pulp must have had, in the earlier stages, about two pounds of water as a carrier. This water must be taken out. And, strangely enough, the process of removal involves the use of an even larger amount of another operator, viz. air. Each pound of water requires more than forty pounds of air to carry it off. The 700 tons of paper produced by one mill during a 24-bour run requires about 1,400 tons of water, and only by the use of 56,000 tons of air is it eliminated!
Think of the volumes involved and of the capacity of the blowers which supply this stream of air! Fortunate indeed are we to have an agent so cheaply available and one so easily disposed of afterwards.
Not so, when we extract valuable oils from shales. The rocky refuse is so voluminous that its disposal presents a problem of first magnitude. The operating plant will fill the landscape with rejected material, and move away from it, rather than transport it away from the plant.
Think of the process of combustion of coal. We commonly
think of the ash as the only "dregs" to be considered. A ton of coal, such
as may be burned in a boiler furnace, may have a residue of 200 pounds
of ash. A small plant burning ten tons of coal per day, therefore, has
one ton of ash each day. The oxygen used by this fuel in the process of
combustion, calculated on the basis of nine tons of carbon, is twenty-four
tons; while the nitrogen which is drawn through the furnace, heated to
a high temperature and thrown out of the slack, totals some eighty-four
Compare this with the one ton of coal ash.
Then again, the air draft openings need to he five times as large because of the presence of this nitrogen, which dilutes the oxygen, slows the process of combustion, reduces the temperature, wastes the heat. Could our grates and boilers stand the temperatures attainable with an atmosphere of oxygen? Will it ever become practicable to eliminate the nitrogen in this process?
The best known of our artificial illuminants convert into light about 4 per cent of the supplied energy. Which is the "side issue," the heat or the light?
Some of these so-called "side issues" may have very important bearings upon the main issue. It is never safe to ignore them until after an analysis which proves their minor importance.
I have to live with myself and so
I want to be fit for myself to know.
I want to be able as days go by
Always to look myself in the eye.
I don't want to stand with the setting sun
And hate myself for the things I have done.
I want to go with my head erect,
I want to deserve all men's respect.
But here in the struggle for health and self
I want to be able to like myself.
I don't want to look at myself and know
That I'm bluster and bluff and empty show.
I can never hide myself from me;
I see what others can never see.
I know what others may never know;
I can never fool myself, and, so
I want to be Self-respecting and conscience free.
—Worth Reading Bulletin.