(How did Dumas colorfully describe those things? I think this is the paragraph: "Yes, a telegraph. I had often seen one placed at the end of a road on a hillock, and in the light of the sun its black arms, bending in every direction, always reminded me of the claws of an immense beetle, and I assure you it was never without emotion that I gazed on it, for I could not help thinking how wonderful it was that these various signs should be made to cleave the air with such precision as to convey to the distance of three hundred leagues the ideas and wishes of a man sitting at a table at one end of the line to another man similarly placed at the opposite extremity, and all this effected by a simple act of volition on the part of the sender of the message. I began to think of genii, sylphs, gnomes, in short, of all the ministers of the occult sciences, until I laughed aloud at the freaks of my own imagination.")
Optical telegraphs! They were a recent invention in Dumas' era,
https://en.wikipedia.org/wiki/Optical_telegraph
(How did Dumas colorfully describe those things? I think this is the paragraph: "Yes, a telegraph. I had often seen one placed at the end of a road on a hillock, and in the light of the sun its black arms, bending in every direction, always reminded me of the claws of an immense beetle, and I assure you it was never without emotion that I gazed on it, for I could not help thinking how wonderful it was that these various signs should be made to cleave the air with such precision as to convey to the distance of three hundred leagues the ideas and wishes of a man sitting at a table at one end of the line to another man similarly placed at the opposite extremity, and all this effected by a simple act of volition on the part of the sender of the message. I began to think of genii, sylphs, gnomes, in short, of all the ministers of the occult sciences, until I laughed aloud at the freaks of my own imagination.")
https://www.gutenberg.org/ebooks/1184