PBEFACE TO SECOND EDITION. XT 



uous girder and braced arch, the course indicated in the pr^- 

 eeding paragraph may be omitted, and then Chap. I., with 

 Appendix, constitutes a course as thorough as can be desired, 

 the student taking first those examples given in the book, and 

 then such others as the teacher may select, and always solving 

 in two ways, by diagram and calculation. He may then take 

 Chaps. II.- V., and now possesses a second method of diagram 

 (Culinann's) by which he may check any or all of the previous 

 cases. In general, a few examples of application to bridge 

 girders, drawing the parabolas for total load (moments) and 

 moving load (shear), will be sufficient. He is now ready to 

 pass on to the Stone Arch, where again suitable problems 

 should be proposed by the teacher and solved under his super- 

 vision. The remainder of the work, including moment of 

 inertia and continuous girder treated by the second method of 

 diagram, will in general be found unnecessary and rather ad- 

 vanced, except in a very full course. 



The course recommended is then as follows, in the order 

 given, chapters in brackets being omitted or not, at option of 

 teacher : 



Chap. I. and Appendix, Supplements to Chaps. VII. (and 

 XIII., Chaps. XIII., XII. and Appendix, XIV. and Appendix), 

 Chaps. II.- V., XV. (XVI., VI., XL). It will be seen that the 

 order recommended for class instruction is quite different from 

 that of the work itself. 



"We would ask teachers examining the book with a view to 

 adoption, to look it over in the order above given. 



With regard to the space occupied in these pages by the con- 

 tinuous girder, and to the opinions held by the writer on that 

 subject, a word of explanation may also not be out of place, in 

 view of the discussion which has arisen since the publication of 

 the first edition of this work. 



It is, of course, understood that we claim, in any case, su- 

 periority for the continuous girder over the simple, only where 

 circumstances render such a construction advisable, and base 

 that claim upon admitted theoretical results as yet not satisfac- 

 torily tested by practice. We do not claim that one should 

 supersede the other. Such a claim represents an extreme 

 view, in our opinion absurd, and which certainly is not advo- 

 cated in these pages, though there have not been wanting those 

 who would attribute it to us. Circumstances connected with 



