I don't know nuthin about furlongs as I didn't meet my first race horse until I was 35. But a "Chain" when I was growing up was called a "Gut Wrapper" or a "Cat Gut" and it went from one side of a logging truck, up over the top of the logs and down to the "Dog" or "Cinch dog". And yes, was 22 ft long. If you "bust a gut", then you had logs spread all over the road. Which was also called a "yard sale".
The "yard dogs" or yard bosses would measure the chains every once in a while... If they were 23' long, they would blow torch them into chunks because they were stretched to the point of being unsafe. Usually these were owned by "Gypos" or Gypsy drivers that moved around from "Show" (logging company) to Show. They usually didn't have enough money to keep up their gear and would get "Blown out" by a dog. A trucker who had a fresh chain in his lock box and pulls it out while the "dog" is "blowing his chain" is "blowing a dog". (don't go there)
The company would weld the pieces back together and thread then through the posts on the side of the road as a railing. It took 80 chains or a "season" to make a mile of railing. No idea if it worked or not.... but didn't stop Heavy from driving his 30 Dodge through the Gut and over the falls just up from Roads End. Falls didn't have a name before but is on the map now as Heavy's Falls. There is a trail head there and a sign that says "Old Iron Springs" 2 miles. When you get up there to the meadow there are some old bed springs piled up and rusted.

Funny guys those loggers.
Dad was "the" Forester at Johnsondale, CA, the last all company town in California.
Loggers have such colorful language.... we would learn a new word and if we got our mouth washed out with soap, we knew it was a great word.