IV PREFACE. 



meeting of the class. Solutions of problems are required to be 

 kept in neat form in a separate book for future reference. 



5th. Numerous references are given so that more extended 

 treatments of different subjects may be readily found by the 

 engineer when occasion requires. 



As a book of reference, it is hoped that it will enable the 

 engineer to put more time than usual upon questions of design, 

 which generally receive too little attention both from the stand- 

 point of economy and strength. A. H. HELPER. 



The above preface was written by Prof. Heller shortly be- 

 fore his death, which occurred February 20th, 1906. 



He had intended to cover, in his book, the common forms 

 of statically indeterminate structures, as well as the three 

 hinged arch and cantilever bridges, as will be seen by repeated 

 references to succeeding chapters which are not included in this 

 book. 



We believe that the fourteen chapters here presented, cov- 

 ering as they do the stresses in all the forms of simple trusses, 

 will be of benefit to the profession as a reference book and to 

 schools as a text book. The manuscript for this book was used 

 by Prof. Heller in his classes in typewritten form, and is believed 

 to be comparatively free from errors. We will be glad to have 

 any typographical or other errors brought to our attention. 

 Columbus, Oct. 9, 1906. C. T. MORRIS. 



THE writer has used this book as a text in his classes for 

 the past nine years, and has found that in many places the con- 

 cise forms of Prof. Heller's statements in the manuscript which 

 he left, and which was published without material alteration 

 in the last edition, were not easily understood by the beginner, 

 and it has been the aim in this edition to expand the explana- 

 tions and to give numerical examples to illustrate the methods 

 where experience has shown this to be necessary. 



There has been little change made in the first four chapters. 

 In this edition, Chapter V includes both Chapters V and VI 



