Appletons* Cyclopedia of Technical Drawing: Embracing the Principles of Construction as Applied to Practical Design; With Numerous Illustrations of . Perspective, and Free-Hand Drawing

Excerpt from Appletons' Cyclopedia of Technical Drawing: Embracing the Principles of Construction as Applied to Practical Design; With Numerous Illustrations of Topographical, Mechanical, Engineering, Architectural, Perspective, and Free-Hand Drawing

In the sale of former editions of this work, it has been found that its success has been largely due to its value as a book of design. Great attention has therefore been given to secure practical illustration of constructions and machines of recent date; the nature of materials in common use has been more extensively treated, and the character and effect of stresses and strains, their kind and direction, more fully explained, with as simple rules as possible to determine them for practical application.

Of late years the science of graphics has become of great importance, and is here fully illustrated in its varied applications, showing not only this method of recording the facts of the statistician, and affording comparisons of circumstances and times, the growth of population, the quantities and cost of agricultural and mechanical production, and of their transport, movements of trade, fluctuations of value, the atmospheric conditions, death-rates, etc., but also in its application to the plotting of formulae for their ready solution, by the draughtsman and designer. For many of the rules in this work the results of the formulae of various authors have been plotted graphically, and the rule given one deemed of the greatest weight, not always by average, but most consistent with our own experience.

In astronomical calculations every decimal may have its importance. It is not so in those of the mechanical or architectural designer; solutions by graphics are sufficient for their purpose, and, simpler than mathematical cal culations, they are thus less liable to error; it is very good practice to use one as a check on the other. It is to be remarked that inaccuracy in facts, and carelessness in observation, are not eliminated from an equation by closeness of calculation, and when factors are not established within the limits of units it is useless to extend the results to many places of decimals. It is of the utmost importance to know at first well the object and purposes of the design, the stresses to which its parts are to be subjected, and the strength and endurance of the materials of which it is to be composed. In establish ing rules for ourselves, be sure of the facts, and that there are enough of them for a general application. Rules are necessary, but their application and usefulness depend largely on the experience of the user, and life must be a record of applications and effects. It is comparatively easy to make a work strong enough; but to unite economy with proportion is difficult.

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