On Thursday, the 10th of October, an in tereßting event took place at the Forth Bridge, this being thecoupling-up of the lower booms of the connecting girder for the great Bouth span of 1700 feet. And th« British Isleß, where the art of metallic bridgo building origi nated, can now claim the possession of the longest span and the strongoat bridge m the world. When completed this girder is to 6 wing from slings on the cantilevers, whioh will permit of the free expansion of the bridge. During construction, however, the ends of the booms of this girder have been rigidly con nected to the cantilevers so as to allow of the building out, the joints being made, as at the Foughkeepsie Bridge, with a wedge coup ling, by whioh, if necessary, the level of the outer ends of the booms could be adjusted. For some days the work had been ready, but the weather was considered to he unfavourable, and it was only on tbat afternoon that the weather became 'sufficiently warm for the work to be undertaken with good prospect of success. So carefully had the work of building been per formed that the two arms, whioh spring from piers 1700 feet apart, met on a perfect level, but as the temperature of the bridge was not as high as was expected, the rivetholes m the booms and connecting plates on the west side, whioh was that exposed to the sun, were half an inch apart, and thoie on the east side were one inoh out of truth. By means of hydraulio jacks, however, the holeg m the western boom were brought fair and the rivetting-up com pleted. On the east side, however, m spite of a pull of 1700 tons by the bydraulio jacks, the rivet-holes were still one-eighth inch apart, and it was then decided to heat the girder. This was done by plaoing waste soaked m naptha m the trough of the girder- and firing it. 