when heated a few degrees above it" and the hot weather had that effect. Samuda's original description of his system had included a metal weather valve that closed over the flap, but this had been omitted on the L&CR, exposing the valve to the weather, and also encouraging the ingestion of debris, including, an observer reported, a handkerchief dropped by a lady on to the track. Any debris lodging in the seating of the flap could only have reduced its effectiveness. Moreover the tallow – that is, rendered animal fat – was attractive to the rat population. An 1859 source reports rats entering the iron tube overnight to eat the tallow, and "hundreds" being killed each morning when the pump was activated for the first train. Delays became frequent, due to inability to create enough vacuum to move the trains, and stoppages on the steep approach inclines at the flyover were commonplace, and widely reported in the press. The Directors now began to feel uneasy about the atmospheric system, and in particular the Epsom extension, which was to have three engines. In December 1846, they asked Boulton and Watt about cancelling the project, and were told that suspending the supply contract for a year would cost £2,300. The Directors agreed to this. The winter of 1846/7 brought new meteorological difficulties: unusually cold weather made the leather flap stiff, and snow got into the tube resulting in more cancellations of the atmospheric service. A track worker was killed in February 1847 while steam substitution was in operation. This was tragically unfortunate, but it had the effect of widespread reporting that the atmospheric was, yet again, non-operational. Sudden end Through this long period, the Directors must have become less and less committed to pressing on with the atmospheric system, even as money was being spent on extending it towards London Bridge. (It opened from Dartmouth Arms to New Cross in January 1847, using gravitation northbound and the Dartmouth Arms pumping station southbound.) In a situation in which public confidence was important, the Directors could not express their doubts publicly, at least until a final decision had been taken. On 4 May 1847, the directors announced "that the Croydon Atmospheric pipes were pulled up and the plan abandoned". The reason seems not to have been made public at once, but the trigger seems to have been the insistence of the Board of trade