PREFACE TO FIRST EDITION. IX 



equal or unequal, offers no more essential difficulty than the 

 calculation of so many separate simple girders. That this is 

 not exaggeration, but accurate statement of fact, a perusal of 

 Chaps. XII. and XIII. will suffice to prove. 



We cannot leave this part of the subject without acknowledg- 

 ing our indebtedness to Mansfield Merriman, C.E., Assistant in 

 Engineering in the Sheffield Scientific School of Yale College, 

 for the formulae of the latter chapter. Mr. Merriman has 

 done for the practical solution of the continuous girder what 

 Weyrauch has for its theoretical discussion. We refer the 

 student to the Supplement to Chap. XIII. for a specimen of 

 his method of discussion. His formulae are simple, entirely 

 free, even in general form, from integrals, and are given in just 

 the shape required in practice. This compactness renders it 

 possible for the engineer to enter upon a couple of pages of his 

 note-book att the formulae required for the thorough calculation 

 of a continuous girder of any number of spans, equal or un- 

 equal ; and this calculation in any particular case proceeds in 

 a manner precisely similar to that of the simple girder, directly 

 and without reference to authorities, tables, points of inflection, 

 elastic line, methods of loading, or any of the " other parapher- 

 nalia with which the subject is usually encumbered." 



It will be observed that here and throughout we have no- 

 where left out of sight analytical processes or methods. The 

 reader who considers the present work as an attempt to super- 

 sede, or even subordinate analytical investigation, misjudges 

 entirely our aim. So far from this, 'we indulge the hope that 

 its perusal cannot fail to render familiar the use of both 

 methods, to bring out their points of difference and relative 

 advantages, to illustrate the one by the other, to enable the 

 reader to check the results of the one by the other, and in any 

 case apply one or both, or a judicious combination of both, as 

 may in such case be most advantageous or desirable. This will 

 be especially noticed in the discussion of the simple and con- 

 tinuous girder and of the braced arch. (Chaps. XII., XIII., 

 XIY. and XVI., and Appendix.) 



As to the use of the work, the practical engineer will find in 

 Chap. I., and that portion of the Appendix relating to this 

 chapter, an easy and simple method of solution applicable to 

 any framed structure having simple reactions, and including 

 thus all varieties of bridge and roof trusses of single span. Iu 



