Transatlantic communication line without electricity

First of all, in a hurry to prevent angry cries, I declare: I do not know the solution to this problem! More precisely: I have some thoughts on this, but there is no beautiful and “correct” solution yet. Consider this post an opportunity to ponder the brain and feel like an inventor.

So condition

Imagine a civilization that has reached our present level of development in all but one: electricity has not been openly. All other technologies not related to electricity, mastered. Physics, chemistry, metallurgy, mechanical engineering, hydraulics, pneumatics, optics, etc. - at your service, but even the simplest battery was not invented.
In such difficult conditions, you are invited to establish a transatlantic communication line. Naturally, all technologies that are somehow dependent on electricity are also not available (forget about the radio!). I propose to evaluate the solution by three parameters:

• Response time. If the transfer time exceeds the time of sending the letter by steamboat, then no one needs such a line.
• Bandwidth. The higher the better, 1 bit per day will not suit anyone :)
• Reliability. It is desirable that the data transfer does not depend on the weather, time of day and other whims of nature. Ideally, the line should be available 24/7.