Measures of distance

[Wilts Wanderer]

Does anyone know why railway measurements of linear distance are in miles and CHAINS? A chain is equal to 22 yards and there are 80 in a mile. I have not come across this unit of measurement in any other walk of life. Any thoughts where it originated and why railways have always used it (or have they? What is the history of its use. Presume some standardisation was agreed at some point possibly by the Railway Clearing House?)

 

[alistairlees]

Surely it is just what was standard in the 1800s? Areas at the time were measured in perches, roods and maybe other things, as well as acres.
Do you play cricket? A chain is the distance between the stumps.

 

[Gloster]

Wasn’t it because when the railways were built the chain was the standard unit of measurement used by the surveyors who laid out the routes. The same information can later be used on the finished line: no point in paying for a new survey. I think that the chain as a unit of measurement went back several centuries before the railways, possibly because a metal chain does not stretch or shrink (to any significant extent), so you have a constant to work with.

 

[Bevan Price]

Does anyone know why railway measurements of linear distance are in miles and CHAINS? A chain is equal to 22 yards and there are 80 in a mile. I have not come across this unit of measurement in any other walk of life. Any thoughts where it originated and why railways have always used it (or have they? What is the history of its use. Presume some standardisation was agreed at some point possibly by the Railway Clearing House?)

It was a real chain, for use by surveyors, and consisted of 100 links, and was adopted as a standard (UK) measure around the 17th century.

https://www.britannica.com/technology/surveyors-chain.

The "foreign" metric system was not widely adopted within UK until the mid- to late- 20th century. Whilst I think that NR now uses the metric system for many purposes, it would be far too expensive (and wasteful) to convert thousands of pages of old documents (and mileposts) to the metric system.

And railways are not the only place to retain "old" units. Horse racing uses the furlong (equal to 10 chains / 220 yards), with 8 furlongs per mile.

 

[Wilts Wanderer]

Surely it is just what was standard in the 1800s? Areas at the time were measured in perches, roods and maybe other things, as well as acres.
Do you play cricket? A chain is the distance between the stumps.

I didn’t know that about cricket, that’s really interesting!

Wasn’t it because when the railways were built the chain was the standard unit of measurement used by the surveyors who laid out the routes. The same information can later be used on the finished line: no point in paying for a new survey. I think that the chain as a unit of measurement went back several centuries before the railways, possibly because a metal chain does not stretch or shrink (to any significant extent), so you have a constant to work with.

Makes a lot of sense, presumably the chains were cast iron.

It was a real chain, for use by surveyors, and consisted of 100 links, and was adopted as a standard (UK) measure around the 17th century.

https://www.britannica.com/technology/surveyors-chain.

The "foreign" metric system was not widely adopted within UK until the mid- to late- 20th century. Whilst I think that NR now uses the metric system for many purposes, it would be far too expensive (and wasteful) to convert thousands of pages of old documents (and mileposts) to the metric system.

And railways are not the only place to retain "old" units. Horse racing uses the furlong (equal to 10 chains / 220 yards), with 8 furlongs per mile.

Thanks for this - yes, I wasn’t wondering why chains are still used, just why they were used in the first place but not seemingly anywhere else such as the road network. Given the historical links between railways and horses I’m surprised that furlongs are not used anywhere.

 

[Mcr Warrior]

Quite convenient that one chain linear distance equals approximately twenty metres.

 

[Gloster]

In order to build their lines railway companies had to get Parliament to pass an act giving them the powers necessary. An important part of the paperwork submitted was a detailed plan of the route; I am not sure of the scale demanded, but it was a large one. I would presume that such detailed information was not needed for the roads.

 

[DelW]

Thanks for this - yes, I wasn’t wondering why chains are still used, just why they were used in the first place but not seemingly anywhere else such as the road network. Given the historical links between railways and horses I’m surprised that furlongs are not used anywhere.

As mentioned in another thread recently, the term "chainage" is still used for distances along roads, pipelines and the like. So it's very likely that pre-metrication (so over 50 years ago now) , roads were also measured in chains.

Chains and furlongs also tied in with area measurement in acres - an acre is 4840 square yards, so equal to a chain by a furlong (or 10 chains by one chain).

 

[Iain Flynn]

Quite convenient that one chain linear distance equals approximately twenty metres.

Approximately the length of a typical bogie coach of steam loco with tender from around 1900 or even earlier onwards

 

[LNW-GW Joint]

Whilst I think that NR now uses the metric system for many purposes, it would be far too expensive (and wasteful) to convert thousands of pages of old documents (and mileposts) to the metric system.

NR uses metric for electrification construction (BR used it for the ECML wiring and any more recent) - the metric distance is on all the masts.
All lines converted to ETCS will use metric distances and speeds (on the route and in the cab) - it started on the Cambrian and will be used on the ECML.
HS1 is metric and HS2 will be, and is used on all the planning maps. So is Crossrail, at least in the new core.
LU has been re-measured in metric for some time (don't know about the speeds).
I think the Cambrian has kept its mileposts along with the new km markers.

Railways abroad weren't always metric.
eg you find early railway measurements in things called Prussian miles (there were others - Austrian and Italian among them).
Area measurement wasn't standard either - there are Cheshire acres for instance, larger than the standard.

 

[Irascible]

Quite convenient that one chain linear distance equals approximately twenty metres.

Given there's ISO metric feet & inches, wouldn't surprise me if someone's used 20m as a metric chain somewhere...

 

[XAM2175]

Given there's ISO metric feet & inches, wouldn't surprise me if someone's used 20m as a metric chain somewhere...

Alas (or perhaps thankfully) the chain was never really used in the construction trade (the main field standardised by ISO 2848:1984), and had in any case fallen out of ordinary use anywhere by the time that standard was promulgated.

Of course nowadays all the "customary" measures are legally defined in metric units so perhaps it can be said that there's a hint of metric in all of it

Chains and furlongs also tied in with area measurement in acres - an acre is 4840 square yards, so equal to a chain by a furlong (or 10 chains by one chain).

Fans of Pink Floyd might already know that last fact

Railways abroad weren't always metric.

It's interesting to note that, in comparison to practice here, the Australian railways were entirely converted to metric at the same time as the national metrication push in the 1970s. You'll still find measurements in MCL scattered around, but all the main lines were re-signposted (often by way of simply moving the existing mileposts).

 

[Irascible]

.

Alas (or perhaps thankfully) the chain was never really used in the construction trade (the main field standardised by ISO 2848:1984), and had in any case fallen out of ordinary use anywhere by the time that standard was promulgated.

There was one relatively well known building built with them ( when it was a BSI, I think ) - was it BBC Shepards Bush?

Monosyllabic Imperial units are great for rough measurements - as soon as you take them anywhere near a computer you soon realise what a PITA they are though.

 

[randyrippley]

Turnpikes and canals were both built using miles and chains.

If you want a more recent example, my father took a builders chain with him when he joined the army in 1942.
Used it to mark out football pitches as they moved through Europe

 

[PaulLothian]

Chains were a part of daily arithmetic in the 1950s/60s. We were very envious of younger relatives who were taught metric weights and measures. On the other hand, I still have the 14x and 16x tables stuck in my mind for Countdown!

 

[DerekC]

My first paid job was as "chain boy" to a surveyor. The measurements were actually taken by steel tape and dumpy level, but the name clearly comes from the same source.