PREFACE. DURING the past year I received from a friend of mine in London some diagrams and descriptions of Suspended and Trussed Bridges, which were part of Mr. Edward Kochs's Patent for "Improvements in the Construction of Beams or Supports applicable to the building of Bridges, Viaducts, Roofs, Arches," etc. My friend asked me for my opinion, and desired me to examine the matter theoretically. These designs, as well as those of the remaining part of Mr. Kochs's Patent, agree all in one thing— viz., that all bracing bars which connect the top and bottom tend to two points; or if one of these points is at an infinite distance, some are parallel. This geometrical design Mr. Kochs seems to have considered very important, and has attached a significance to it which I think it does not deserve, and which an unprejudiced observation will confirm. Another point, however, which in the said description was clearly expressed, showed that the construction of Bridges, besides this geometrical arrangement, contained a decidedly novel thought, even although Mr. Kochs had not fully recognised its whole importance. |