'Estimate of expense of making a road across Chat Moss' 20th Jun 1829

OBJECTS OF ENGINEERING- Chat Moss

'Estimate of expense of making a road across Chat Moss' 20th Jun 1829
‘Estimate of expense of making a road across Chat Moss’ 20th Jun 1829

Chat Moss estimate- now available online

The crossing cover Chat Moss was one of the toughest engineering challenges on the route of the Liverpool & Manchester Railway, the world’s first inter-city passenger line. The Moss is formed from a huge swamp of mossy peat, and George Stephenson and his team had to traverse it in order to create the service. Written by John Dixon, this innocuous piece of paper in our collections actually details the cost of the challenge, £78,320 for 4 miles. That is the equivalent to a purchasing power of £6,013,000 in 2013! The estimate is only for the timber, it excludes aspects such as nailing down the planking. John Dixon was the Railway’s surveyor.

The original route for the line did not cross Chat Moss but this had to be altered due to objections from the Bridgewater Canal trustees (whose business was likely to be adversely effected by the railway) and Parliament. Stephenson’s solution to making the crossing was to spread the loads over a wide area and distribute the pressure; forming a floating raft on top of the peat upon which to build the railway track bed. The peat and moss ranges from 4.6-11m deep, swelling in wet weather and shrinking in dry. It was so wet that for every cubic metre of embankment formed, 2.4 cubic metres of raw peat was used (allowing for water to drain when the turf was compressed). Heather bundles, brushwood mattresses and timber hurdles 2.4-2.7m long and 1.2m wide were placed in layers to form the raft. Ballast, sleepers, chains and rails were then fixed over the timber base. Old tar barrels were joined end-to-end to make wooden culverts to drain the two parallel side ditches, 14.6m apart.

Work was surprisingly successful, if hard for workers who had to strap wooden planks to their feet so as not to sink! Only at the east end were there issues, as materials kept being absorbed by the ground. Eventually dried peat, dried moss, earth and some cinders were used to stabilise the ground sufficiently; being lighter than ballast they enabled the raft to float more easily.

Alongside debates about the construction of the Railway, were debates about what to run on them. George Rennie, his brother John Rennie Jnr and Charles Blacker Vignoles advocated a horse-drawn railway. James Walker and John Rastrick suggested stationary steam engines be placed at fixed locations to haul trains on chains. Stephenson argued for steam locomotives, for their speed end efficiency. Four months after this estimate was drawn-up, Robert Stephenson (George’s son) and Joseph Locke won the Rainhill Trials; the Rocket steam locomotive hauled 13 tons (three times its own weight), it averaged 12 mph (19 km/h), with a top speed of 30 mph and was the only contender to complete the Trials. (The Trails were a competition to find the right engines for the Railway, five engines competed, running back and forth along a mile length of level track at Rainhill, in Lancashire.

Two more months on and the line was complete, on New Year’s Day 1830 Rocket was the first to travel over it. The railway is double track standard gauge throughout its 31 mile (50 km) length; 4 ft 8 12 in (1,435 mm). This became the standard gauge used in railway construction.

View of the railway across Chat Moss (IMechE collections, END/10/5/1/6)

Archives, Institution of Mechanical Engineering

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