PREFACE TO SECOND EDITION. 



THE present Edition of this work has undergone careful re- 

 vision and correction, and no pains have been spared to render 

 it free from typographical errors, and worthy of the very cor- 

 dial reception it has thus far met with. For this reception the 

 Author would express his gratitude both to the Profession and 

 to the faculties of the several colleges who have already adopted 

 it as a Text Book. 



To these and others who may examine it with a view to in- 

 troduction, a word or two may be allowed us. 



The work was not intended to be read through in sequence 

 by any class, but must be used with reference to the degree of 

 preparation of the students, to the time at disposal, and to the 

 relative importance and relation of the various subjects treated. 

 The logical order of presentation requires a certain order in the 

 development of the subject as a whole, but it by no means fol- 

 lows that this order should be preserved by the student, or that 

 he should be acquainted with the whole. In fact, some of the 

 subjects treated of are best taken up by the student at a later 

 period, when better prepared for their comprehension ; others 

 are best omitted at least in the first reading, and others again 

 may even be omitted entirely as of minor importance, and the 

 student left to pursue them for himself, as taste or the exigen- 

 cies of practice may demand. In this latter respect, as well as 

 in the completeness with which the several topics are discussed, 

 the work is intended to serve as a book of reference. As a 

 Text Book, it is designed to teach those students possessing the 

 knowledge of mathematics and mechanics usual to the senior 

 classes in our technical schools and colleges, how to find the 

 conditions of stability in every kind of structure of common 

 occurrence ; and this not alone by graphical construction, but 

 also by calculation as well. Structures of less common occur- 

 rence may or may not be then taken up, according to the 

 ability of the class and the time at disposal. With the above 

 end in view, the teacher will find it not merely desirable but 



