PREFACE. 



The author's first railroad bridge specifications were pre- 

 pared over a quarter of a century ago. From time to time 

 these have been revised to meet the requirements of increas- 

 ing train loads and the improvements in material and 

 methods of construction. This edition is the tenth revision, 

 seventh of those published in his own name. 



While these specifications are " general " in their require- 

 ments, they are more especially intended to cover ordinary 

 railroad bridges or those resting on two supports only. For 

 special structures or those having special or unusual condi- 

 tions and requirements, they should be supplemented by 

 clauses suitable for the particular case. 



Specifications have no executive functions. Unless intel- 

 ligently supervised and executed, they have little value. The 

 author's experience forces him to the conclusion, that plans 

 and structures fully complying with the specifications^ are 

 limited in number; many are defective in important details. 



We are now at a period, when railroads will demand 

 bridges capable of carrying the maximum possible train 

 loadings, not only safely, but rigidly. There will be here- 

 after no increasing train loads to cover or excuse the faults 

 of design, details of construction or inferior material. 

 Bridges of the future must be relatively better than those of 

 the past. Any false economy by scrimping the details or 

 ; an inferior class of material will not redound to the 

 credit of the Bridge Engineer. 



