"Ploughed fields, at all events," replied Michel Ardan. "But what ploughmen these Selenites must be, and what gigantic oxen they must harness to their ploughs, to make such furrows!"
"They are not furrows, they are crevices!"
"Crevices let them be," answered Michel with docility. "Only what do you mean by crevices in the world of science?" Barbicane soon told his companions all he knew about lunar crevices. He knew that they were furrows observed upon all the non-mountainous parts of the lunar disc; that these furrows, generally isolated, were from four to five leagues only; that their width varies from 1,000 to 1,500 metres, and their edges are rigorously parallel. But he knew nothing more about their formation or their nature.
Barbicane watched these furrows through his telescope very attentively. He noticed that their banks were exceedingly steep. They were long parallel ramparts; with a little imagination they might be taken for long lines of fortifications raised by Selenite engineers.
Some of these furrows were as straight as if they had been cut by line, others were slightly curved through with edges still parallel. Some crossed each other. Some crossed craters. Some furrowed the circular cavities, such as Posidonius or Petavius. Some crossed the seas, notably the Sea of Serenity.
These accidents of Nature had naturally exercised the imagination of terrestrial astronomers. The earliest observations did not discover these furrows. Neither Hevelius, Cassini, La Hire, nor Herschel seems to have known them. It was Schroeter who in 1789 first attracted the attention of savants to them. Others followed who studied them, such as Pastorff, Gruithuysen, Boeer, and Moedler. At present there are seventy-six; but though they have been counted, their nature has not yet been determined. They are not fortifications certainly, anymore than they are beds of dried-up rivers, for water so light on the surface of the moon could not have dug such ditches, and there furrows often cross craters at a great elevation.
It must, however, be acknowledged that Michel Ardan had an idea, and that, without knowing it, he shared it with Julius Schmidt.
"Why," said he, "may not these inexplicable appearances be simply phenomena of vegetation?"
"In what way do you mean?" asked Barbicane.
"Now do not be angry, worthy president," answered Michel, "but may not these black lines be regular rows of trees?"