Why does a line sometimes appear following the first letter of a name in old novels such as Les Miserables?

i.e. the author may write of "Mr. M---------" or "the town of G---------"

Why does a line sometimes appear following the first letter of a name in old novels such as Les Miserables?
it also goes back ot the puritan england days when it was considered indecent to write fiction so all fiction was writen under the guise of a story which was told to the author by someone else, you would write like that becuase it would make it impossible for the censer or political enemies of the write to check to see if the person or town was real or not its easly to check on Mr. Maxwell of Georgetown, but it would be impossible to check for the existance of Mr. M____ of G_____
Reply:It's an old-fashioned literary convention. The author is trying to make it seem as if they are naming a real person or real place, but want to protect the "anonymity" of the person or town. It was an early attempt at injecting realism into fiction writing, at a time when politeness and tact mattered a little more than it does now.