This was principally because the logs, which were often left for long periods in the water due to the poor and infrequent steamer services, became infested with teredos or shipworms.
The bridge supports had been weakened by the marine mollusc teredo navalis (commonly known as shipworm).
Wooden pilings to support the platforms were vulnerable to teredo worms.
They were riddled with tubes made by burrowing teredo worms.
Thus, it was also used to sheathe the piles of piers in tropical seas, as a protection against teredo shipworms, and in locomotive tubes.
