Just a quick one today. This is another one of those stories that floats around Victorianist circles. I don't recall the first place I heard it.
In 1859, there was a geomagnetic storm so enormous that it produced auroras (on August 28th and September 2nd of that year) that are considered to be the biggest and most spectacular in recorded history.
The auroras were so widespread and so vivid that they could be seen over most of the globe, including the far east (parts of China, Japan and Australasia), all over North America, and all over Europe. It was reported by the New York Times that in Boston on Friday 2 September 1859 the aurora was "so brilliant that at about one o'clock [a.m.] ordinary print could be read by the light".
Since telegraphs were very widespread at this point, the geomagnetically induced current from the aurora influenced telegraph operation so much that it allowed people to see just how strong this one was:
Telegraph operators could switch off their power supplies and still be connected. The following conversation occurred between two operators of the American Telegraph Line between Boston and Portland, Maine, on the night of 2 September 1859 and reported in the Boston Traveler:
Boston operator (to Portland operator): "Please cut off your battery [power source] entirely for fifteen minutes."
Portland operator: "Will do so. It is now disconnected."
Boston: "Mine is disconnected, and we are working with the auroral current. How do you receive my writing?"
Portland: "Better than with our batteries on. – Current comes and goes gradually."
Boston: "My current is very strong at times, and we can work better without the batteries, as the aurora seems to neutralize and augment our batteries alternately, making current too strong at times for our relay magnets. Suppose we work without batteries while we are affected by this trouble."
Portland: "Very well. Shall I go ahead with business?"
Boston: "Yes. Go ahead."
The conversation was carried on for around two hours using no battery power at all and working solely with the current induced by the aurora, and it was said that this was the first time on record that more than a word or two was transmitted in such manner.