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LONDON:

PRINTED BY VIRTUE AND CO., LIMITED,

CITY ROAD, LONDON.

PREFACE.

In writing the present treatise, my object has been to produce a work dealing comprehensively with the subject of materials and their use in certain branches of constructive art, viz. the massive works usually intrusted to civil engineers and architects, and throughout I have carefully avoided the introduction of the higher branches of mathematical investigation ; and in so doing I have not omitted problems of the classes usually treated by high mathematical processes, but have substituted simpler, but equally convincing, lines of argument for the more abstruse processes of analysis.

It will be found that algebraical arithmetic, or simple forms of equations, supply the basis of calculation, and this basis is indeed amply sufficient for all the theoretical reasoning that is called for in the consideration of the practical problems engaging our attention.

From the above remarks it will be seen that the work is designed especially for all those readers who desire to become thoroughly acquainted with the theories of structures and the practical application of results in the simplest way, and not as a mathematical exercise. It may be advisable to say a few words in explanation of the stress I lay upon the importance of this simplicity of calculation. There are comparatively few of those entering upon a mechanical profession who are thoroughly accomplished mathematicians, and once launched upon the business of life—or what is equivalent to it, the probationary term which precedes actual remunerative employment—the tyro will not desire to give time to the study of abstruse science, beyond the point where it ceases to be absolutely necessary for his purposes ; and there are many who have only learned these exact sciences bit by bit as they have found them necessary.

Another matter of common consideration is, that even in those who have become proficient at school and college in pure mathematics, this knowledge, unless sedulously maintained and reinforced by after-study, rapidly decays, and is often only with great difficulty revived; and the time absorbed by this reinforcement or revival is generally required for the purposes of more directly practical study.

Although all structures should combine in themselves both strength and stability, I have, for the sake of clearness, separated the two classes as far as can conveniently be done for theoretical investigation; showing, however, their necessary connection in suitable places.

In the examples taken to illustrate the methods of calculation, I have carefully selected cases such as occur in every-day practice, and carried them through, in order to leave no doubt or difficulty as to the practical application of the formulæ.

In conclusion, I would add that this work is not intended in any way as an elementary introduction only to the science of construction, but deals fully and finally with all the subjects included in its syllabus.

FRANCIS CAMPIN.

CONTENTS.

PAGE

CHAPTER I.-INTRODUCTORY-CONSTITUTION OF MATTER—Elas

TICITY—INTERNAL FORCES—EXTERNAL FORCES

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CHAPTER II.-GENERAL PROBLEMS-MOMENTS

BALANCED FORCES

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CHAPTER XII.-PRACTICAL APPLICATION OF FORMULA

145 CHAPTER XIII.- ECONOMICAL PROPORTIONING OF STRUCTURES. 172

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PAGE CHAPTER XX.-STRENGTH OF MATERIALS .

236 TABLE 1.-ULTIMATE TENSILE RESISTANCE OF TIMBER 243

2.-ULTIMATE RESISTANCE OF TIMBER TO CRUSHING 243 3.-TRANSVERSE RESISTANCE OF TIMBER

244 4.-ULTIMATE TENSILE RESISTANCE OF METALS 244 5.-ULTIMATE RESISTANCE OF CAST IRON

245 6.-ULTIMATE RESISTANCES OF BUILDING MATERIALS TO CRUSHING,

245 7.-MODULUS AND LIMIT OF ELASTICITY OF MATERIALS

246 8.-ULTIMATE AND WORKING RESISTANCES OF VARIOUS MATERIALS

247

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