EDUCATIONAL PROCESS OF TRAINING AN ENGINEER. 575 
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in bearing loads; in short, to put himself as nearly as possible in such 
a condition that he knows what is the extent of our knowledge of the 
facts, as shown by experiment, in regard to the behavior of the materials 
of construction—wood, iron, steel, stone, cement, concrete, etc.—when 
subjected to such loads as they have to bear in practice. 
There are a good many cases where some people, who think they are 
calculating everything with all due care, neglect to determine correctly 
the forces acting on a piece, or the stresses produced by those forces. A 
few examples will serve to illustrate. Take the case of one of the columns 
of a building. When the greatest load per square foot covers the entire 
floor above, the resultant of the load on that floor acts along the center 
line of the column, and the stress per.square inch due to this load is uni- 
formly distributed over the section. When, on the other hand, the floor 
on one side is fully loaded and the floor on the other side is not loaded, 
then the total load is less than it was in the other case; but its resultant 
does not act along the center line of the column, but is eccentric, and the 
consequence is a tendency to bend the column. 
When a column in a building is to be calculated, we should determine 
what is the greatest stress on one side due to having as great an eccentri- 
city of load as is possible to be attained in the use of the building, and we 
should see that the dimensions of the column are such that this greatest 
stress should not exceed safe limits. 
Another illustration is to be found in the matter of fly-wheels of steam 
engines. Every once in a while we hear that some fly-wheel has burst ; 
the pieces have, in consequence of the breakage, been hurled in all direc- 
tions, carrying death and destruction in their paths; people are killed, 
buildings demolished, and property destroyed. In several cases of wheels 
which I have examined, the stresses in the bolts uniting the separate por- 
sions of the rim and the stresses in the separate portions of the rim near 
she joints were greater than a proper regard for safety would allow, and 
greater than the designers of the wheels would have allowed had they 
realized their existence. The difficulty was that the designers had 
aeglected to make allowance in their computations for the fact that the 
volts were not placed in the line of direction of the resultant tension, but 
on one side of that line. 
Another case where the disaster came about in consequence of having 
neglected to consider the effect of an eccentric load is to be found in the 
Bussey bridge accident which occurred a few years ago, where one of the 
hangers had a very eccentric pull upon it, while it was only strong enough 
50 bear the load if it had been central. This disaster caused heavy 
destruction of property and large loss of life. 
From the foregoing it is evident that the man who trusts to formule 
derived from some handbook to make his calculations for the strength of 
materials, while he does not know the principles upon which those formule