The present work is a treatise on the Strength of the Materials used in Construction, considered in connection with the instruments and methods by which the mechanical properties of materials are investigated experimentally.<br><br>The data on which the engineer relies in designing structures cannot be fully understood without some knowledge of the procedure by which they are ascertained. Also, for several reasons, a knowledge of the methods of testing has become of late of greater importance. With the introduction of new materials, the engineer has been forced to make more use of the testing-machine, both in estimating a constructional value of materials and to escape the danger of employing material which is unsuitable. A considerable advance has been made in the construction of all the apparatus used in testing, the operations of testing are carried out with more care and skill. Lastly, the establishment of Engineering Laboratories, in connection with Schools of Engineering, has made experimental investigation an essential part of engineering education.<br><br>The following treatise consists of three parts.