6] 



ignorance." When it is doubtful just how great a resistance can be withstood by 

 a given bulk of material, we make success certain by building many times 

 stronger than is really necessary. If we could know at the outset the exact value 

 of the stresses involved and the actual strength of the materials to be employed, 

 it would become obvious that such a practice as this could give no additional 

 security, and its result would be wastefulness. 



In the domain of machine construction the same general principle applies. 

 The demand is everywhere made for machines that will act with a higher degree 

 of efficiency ; that is, do their work with less wear and tear and at a lower run- 

 ning expense. There is no lasting market for inferior gocds, and success in 

 competition is to be obtained as the result of merit. Thus it is that designing 

 engineers who give their thought and skill to planning great bridges, buildings 

 and machines are successful in proportion to their ability to simplify and cheapen 

 and at the same time perfect, while all unite upon the general principle that a 

 bridge must not only stand, but it must also involve a minimum of material, and 

 a machine must not only run, but must do its work with the highest degree of 

 efficiency. 



It is clear, therefore, that what is needed in engineering work is a more 

 perfect knowledge of the materials and forces involved. This is not a reflection 

 upon the knowledge of the past, but a suggestion that its fund is insufficient for 

 the future. The engineering of the last quarter century has done much to make 

 definite matters which were before but little understood. Facts have been gath- 

 ered and compared, and from them theories have been deduced. Failures are 

 fewer and the efficiency of structural work, and of machines of every sort, has 

 been increased. But the end is not vet. To-day, more than ever before, the 

 attention of the whole engineering world is directed to methods of improving and 

 saving. Its efforts are put forth in response to the demands of a more exacting 

 clientage, and this clientage is the public. It is evident that everything which 

 contributes to the perfection of engineering methods must benefit the peojile and 

 must arouse their interest, for it is the people who finally reap the advantages, as 

 well as pay the price. Hence public interest in the work of the engineer is keen 

 and critical, and will always sustain any serious movement which promises t<5 

 advance true practice. Such a movement presents itself in the establishment of 

 laboratories devoted to engineering research. 



When all forms of mechanical construction were crude it was possible to im- 

 prove by the mere application of experience, but as construction became more 

 refined it was necessary to examine with greater accuracy and to proceed with 

 greater care. The crude stage in engineering is now a thing of the past, and 



