XVI PREFACE TO SECOND KDITTON. 



method of erection, etc., may certainly be imagined in which a 

 continuous girder presents advantages not possessed by the 

 simple. It finds, at least, direct application in the pivot span. 

 When such circumstances arise, the engineer, we take it, will 

 not find fault with a full and thorough discussion of the subject, 

 such as here given, and he may even find the method of solu- 

 tion which we recommend of service. The continuous girder 

 has then its proper place, if we can only ascertain it, just 

 like the bow-string girder, arch, suspension system, etc., which 

 also may, under proper circumstances, be preferred to the sim- 

 ple girder, without necessarily detracting from the just merits 

 of the latter. The others have been tested by practice, and 

 their relative advantages pretty clearly settled. When the 

 same shall have been done for the continuous girder, the dem- 

 onstrations and method of solution here given can also be 

 estimated at their true value. Should practice show the sys- 

 tem worthless and theory fallacious, we hold ourselves ready at 

 any moment to strike out the portions affected. Meanwhile 

 the method of solution here given was at the time of publica- 

 tion entirely new ; the formulae were an advance upon any up 

 to that time presented ; the subject, heretofore difficult, was 

 rendered easy of solution, and brought out in a very striking 

 manner the powers of the graphical method, the value of which 

 is of course unaffected by the fate of the theory of continuity. 

 Until then, practice decides very clearly against the system ; it 

 has very properly a place in a work professedly treating of 

 framed structures. 



As to the merits of the case, the theoretical saving is cer- 

 tainly large enough to justify careful consideration and trial, 

 and our theoretical results have never been called in question. 

 How much, in any case, of this theoretical gain can be realized 

 practically, it remains for intelligent practice to decide the 

 full solution is beyond the reach of analysis. To assume, as 

 some do without experiment, that the objections to the system 

 and to the theory, however valid in themselves, do actually 

 cover or more than cover the large gain indicated in some cases 

 by theory, is practically to beg the whole question. 



To assume, as some have, that because this large theoretical 

 saving is not found in certain special cases of small span, where 

 indeed it was not to be expected, that therefore it is not to be 

 obtained in other cases, is to evade the question. For almost 



