Telegraph lines

[Guinness]

Well, most of the time, the constraint is how fast a ship can spool out the cable, I guess. I found this link:

http://www.atlantic-cable.com/Article/Easton/

Under good conditions of weather with a flat ocean bottom, laying can proceed as fast as 8 knots.

So maybe cut that in half to get an average. 96nm a day? After that, you have time to terminate it, test it, etc. which would likely be static no matter how long the cable is.

So, for a 3000nm cable, you get about 32 days to run it (using the 4knot measurement) plus time to terminate, test etc. I'd say that would have to be at least 2 months, maybe more.

[The Rock Doctor]

I've just been perusing the same site.  Different part, though.

That's a good enough estimate, though - I wasn't sure if these would be done on a scale of weeks, months, or years.

Thanks - I'm off to make plans.