SYDNEY PHENOMENON

Taranaki Daily News, 14 February 1931, Page 23 (Supplement)

SYDNEY PHENOMENON

HARBOUR BRIDGE “GHOST.”

ENGINEERS’ EXPLANATION.

Sydney, Feb. 5.. The Sydney 'Harbour Bridge, now rapidly nearing completion, has a “Ghost.” At regular intervals eerie wails are heard, but unfortunately for those who have a leaning to the supernatural, the engineers have a simple explanation. The uncanny sounds were first heard on the approach spans. They began faintlv, then rose in volume, and then died away. They were first attributed to the siren of a vessel passing beneath the arch, but the persistence of the sounds soon attracted more minute attention. Engineers were informed that strange noises had been heard, They endeavoured' to find a solution of the phenomenon. It was not easy. Several theories were advanced and as quickly rejected. It was suggested that the riveting machines were reacting on certain members, causing them to take up the vibration in m the same manner as a tuning fork, ibis was soon discounted for the sounds came strongly even when there were no riveters at work. It was then suggested that gusts of wind were responsible. On the roadway section there are several vertical pipes for drainage purposes, and it was thought that, under the influence of the wind, they were acting as the pipes for some huge organ. The occurrence. of. the sound on a perfectly still day exploded that theory. Now a very simple solution of the mystery has. been found. It has been observed that the wailing has been heard only on days during which the temperature has varied greatly. On a cloudy dav, broken by short periods of strong sunlight, the wails are particularly noticeable. On such days there is considerable movement at the expansion, jxnnts of each steel truss. Due to the weight of steel bearing on the plates on which each truss slides, friction is considerable. Movement then takes place in a series of forward and backward jerks. .1 his irregular movement sets up vibrations in the members constituting the framework of each truss, which acts as an enormous tuning fork. Of course, there are still some people who prefer- to believe that there is a bridge “ghost,”