PROFESSOR AT THE POLYTECHNIC SCHOOL AT AIX-LA-CHAPELLE. E. & F. N. SPON, 46, CHARING CROSS. NEW YORK: 446, BROOME STREET. TRANSLATOR'S PREFACE. THE first edition of Professor Ritter's work, of which the Some interesting problems are discussed in the Eleventh Chapter, and are possibly not generally known in this country. It is required to determine the form a structure should have to fulfil given conditions as regards the stresses. These problems give a considerable insight into the manner in which the stresses are distributed amongst the various bars of a structure, and show also that comparatively small changes in the form may produce great changes in the stresses. The effect of changes of temperature on the deflection and on the stresses in a "composite structure" is treated at some length in the Fourteenth and Sixteenth Chapters. The theory of loaded beams is only touched upon-in fact, only those cases are considered which are required in the various examples. The Sixteenth Chapter contains a very instructive example of a composite structure consisting of a pair of braced girders combined with suspension chains. It should be observed, however, that Herr Hugo B. Buschmann, in a pamphlet 'On The substance of the first two chapters was published previously in the 'Zeitschrift des Architecten- und Ingenieur-Vereins für das Königreich Hannover,' vol. vii., No. 4. 8/11970 the Theory of Combined Girder and Suspension Bridges,' takes exception to the manner in which the equations (§§ 56 to 61) giving the stresses in the girders produced by the moving load are arrived at. In the preface to the third edition Professor Ritter says: "Herr Buschmann maintains that these equations depend on arbitrary assumptions, and thinks to prove their unsoundness by remarking that under certain conditions of loading, namely, when both ends of the girders are loaded, they give a negative bending moment at the centre of the girders, or, in other words, the girders would be bent upwards. Thus the radii of curvature for the central part of the suspension chains would be increased, and this requires a diminution of the length of these chains, which is evidently absurd. This conclusion is, however, incorrect. Herr Buschmann overlooks the fact that exceedingly small changes in the form of the suspension chains are under consideration, and that therefore not only the vertical but also the horizontal displacement of each element of the chain must be taken into account. doubt if the chord of the arc whose radii of curvature are increased did not alter, the length of this arc would be diminished. But if at the same time the length of the chord increases, not only may the length of the arc remain unaltered, but it may even be lengthened; and this is what in reality occurs, owing to the horizontal displacement of each point of the chains, not only in the case under consideration, but also for all positions of the loads." Without In some few instances Professor Ritter does not agree with the more recent English practice, notably so in his estimate of the wind-pressure on roofs. These instances have been pointed out in notes added to the text and in an Appendix. Gibraltar, 1879. H. R. S. 14 § 9. Application of the Method of Moments to the Calculation of the Stresses in Braced Girders having Parallel Booms .. § 10. Braced Girder of 16 metres Span, composed of single Right-angled § 12. Remarks on the Degree of Accuracy of the Assumptions made with regard to the Distribution of the Loads § 13. Braced Girder with Equilateral Triangles, or Warren Girder (Railway |