NUMERICAL CALCULATIONS.

addition to the name and the date, all calculations shouldaccompanied by a complete record of the object and purpose

of

the calculation, the apparatus, the assumptions made, the

data

used, reference to other calculations or data employed,

etc.,

to

in short, they should include all the information requiredmake the calculation intelligible to another engineer without

further

information besides that contained in the calculations,

or in the references

given therein. The small amount of time

and

increased

work required to do this is negligible compared with theutility of the calculation.

Tables

and curves belonging to the calculation should in

the

same way be completely identified with it and contain

sufficient

data to be intelligible.

d.

167.

Reliability of Numerical Calculations.The most important and essential requirement of

numerical

engineering calculations is their absolute reliability.

When

making a calculation, the most brilliant ability, theoretical

knowledge and

practical experience of an engineer are

made

useless, and even worse than useless, by a single error in

an

important calculation.

Reliability

of the numerical calculation is of vastly greater

importance

in engineering than in any other field. In pure

mathematics

example which

an error in the numerical calculation of anillustrates a general proposition, does not detract

from the

interest and value of the latter, which is the main

purpose; in physics, the general

the'

law which is the subject ofinvestigation remains true, and the investigation of interest

and

use, even if in the numerical illustration of the law an

error

is made. With the most brilliant engineering design,

however,

if in the numerical calculation of a single structural

member

an error has been made, and its strength thereby calculated

wrong,

the rotor of the machine flies to pieces by centrifugal

forces,

engineer.

or the bridge collapses, and with it the reputation of theThe essential difference between engineering and

purely

scientific caclulations is the rapid check on the correctnessof the calculation, which is usually afforded by the per

In

be