Using Roman Technology? Could a mechanical engineer build some type of machine to make copper wire? What about electricity? How difficult would it be to build a crude generator near a water source with enough power to connect the empire by telegraph?
I was thinking instantaneous communication with the frontiers would allow the legions to be deployed much more rapidly, possibly enough to shift the power balance enough to save the late Western Empire.
To make wire I think you would need an extrusion press. Building something like that would take as much time as forming wire by hand probably.
I think I could, given the right tools and time, make a crude generator. I’m not sure I could create over-the-air telegraphy though. Can we also hard wire that? 
Nothing too outrageous needed, I’d say. The Romans had copper. They had experience in drawing out fine wires of copper (or gold) for jewellery or other decorative uses. Batteries aren’t very challenging technology if you already know about them. I don’t know of anything involved that couldn’t be built with materials and techniques available to the Romans.
Heck, given time the engineer could probably build simple radio transceivers (with or without a couple of coconuts.)
Impractical to lay thousands of miles of copper wire. Some kind of relay system might work though; Heliograph, semaphores and shutters and the ubiquitous “The enemy are coming, light the bonfire” were probably as good as it could get.
Forget about an electric telegraph – it’s easy to build a mechanical telegraph. L. Sprague de Camp had his hero, Martin Padway, who was sent back to the late Roman Empire, do just that in his classic novel Lest Darkness Fall. The hard part was persuading people to use it and keep using it.
You could build an electric telegraph, I suspect, but you’d probably want a lot of help in obtaining and refining the chemicals needed and in drawing the wire and coating it with insulation. Modern wire-pulling hadn’t been invented in the Roman Empire, so you’d have to do some inventing. You wouldn’t have rubber or plastic for insulation, so you’d have to come up with a substitute (polymers from linseed oil?) or else string a LOT of tiny beads on your wire as insulation. It might be easier to do without insulation and make a lot of glass insulators to put on your telegraph poles so that rainwater doesn’t short out the signal.
I suspect you could do it, with a lot of ingenuity and compromises. But it’d take longer and more work than you think it would.
You would need strong, insulated wire for the distance runs, very fine copper wire to make coils, and a relatively strong source of DC power. All are accessible, as above. The rest (fabricating keys, clickers, insulators, etc.) is within the capabilities of the era.
Mechanical telegraph system:
Lest Darkness Fall:
Padway decided his semaphore telegraph system would only be practical if they had telescopes, so he also had to, with some difficulty, convince a jeweler to make glass lenses. But all in all, a semaphore line would be much more practical than an electrical telegraph, given Roman technology (or what we know of it – the Antikythera Mechanism is a clue that there may have been more advanced technology at the time than we’re aware of).
By cable is what i had in mind. Not radio.
It would be more practical, requiring fewer stations, with telescopes. But you don’t need telescopes for such a system. I believe that the French system used in Napoleonic times didn’t rely on telescopes.
Making good-quality glass and grinding precision lenses to make a good telescope is a pretty nontrivial thing in itself. There’s convincing evidence (to me, at any rate) that Romans had optical lenses, as well as glass globes filled with water to use as magnifiers. But that’s a long way from having a telescope.
Yeah, but that can’t give you detailed communication in the same way as a telegraph. If your backup is 7 days march away, it’s helpful to know “we’re on our way,try to hold out” or “we have our own problems here, you’re on your own”.
The Napoleonic system certainly could since it could transmit several characters per minute, so these messages could be passed on from one tower to another in only a few minutes given a smart enough code.
The hard part, of course, is getting the resources to build a demonstration model that works well enough to convince someone to fund a full-scale system. And even then, the cost of metal at the time might make a full-scale system too expensive to realistically build.
After that, I think the next hard part is knowing all the details of a good system. I mean, without looking anything up, I know enough about electricity and circuits to knock together a battery and a toy across-the-room telegraph, but it would take me a long time to develop and work out the amplification/repeating devices and other bits and pieces that make long-distance telegraphs feasible.
Right, it’s just a question of expense. Even a crappy telescope in each tower probably reduces the number of towers by at least 2 or 3 times. If telescopes are possible at all, the cost of a telescope is probably much less than the cost of a tower.
Yes, in the book Padway had some trouble with that.
How so? Given the right lenses, a telescope just requires mounting a couple of them in a tube. It may have chromatic and spherical aberration, but it would be good enough to see a semaphore from farther than you could see it with the naked eye.
Overhead telegraph wire was not insulated. A couple of percent zinc or tin could provide extra strength, the copper probably already had impurities. Magnet wire was coated (still is) with varnish/lacquer. Drawing out the wire would be a challenge. It can be done with multiple passes through rollers, but you need smooth, steel rollers. Maybe hard stone would work. And that really doesn’t get small diameter, round wire, that needs a die and some pulling power, although block and tackle might do it.
Dennis
I almost wonder if building a primitive radio transmitter/receiver might be easier, since no one else would interfere or intercept over the air.
The Marconi system used on steamships used a crude electrical spark to send code.
If you see pictures of old ships, you’ll see two masts - you may or may not see the wires strung between them - that was the Marconi’s antenna.
According to the wiki article, the Napoleonic semaphore system was developed by the Chappe brothers, and it says “The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message”. This is describing an early prototype, and it doesn’t say that their later systems continued to use telescopes, but it’s hard to see why they’d stop using them.
This article seems well researched, and says “The lines between cities were composed by a series of towers (stations), 10-15 km apart, equipped with a pair of telescopes and a semaphore…”
This BBC article (admittedly not the most authoritative source) says “In each hut, a single operator had the task of surveying his neighbours by telescope.”
It’s not really an important point, but it seems that the Napoleonic system did use telescopes.
Fiber optics are manufactured with a draw tower; that it, molten glass is dripped out of a crucible, and as gravity pulls it down, acceleration and surface tension turn it into a thin cylinder. The cooled fiber coils up at the bottom. I wonder if it’s possible to do the same with copper wire. Might not be as fast as the die method, but doesn’t require hardened steel and precision machining.
Heck, maybe they could just make fiber optics. Wouldn’t have great range with the quality of glass they had available, but it might be good enough with concentrated sunlight on one side and a guy in a dark room on the other.