09:27 Jan 13 

I think Jack is right. "Plane" here probably means "two-dimensional" and has nothing to do with "plain" meaning either "simple" or "a flat land". It is presumably a geometrical term.

09:20 Jan 13 

Have I been asleep, or has language moved on?

Why has no-one pointed out that "plain folk" can mean those that are simple, as well as those that live in the /on the plain(s)? Here, "plane" is (simply) misleading,as it is used today for a flat surface, and has AFAIK nothing to do with a geographical "plain", which is more or less flat(tish) land (flatlands, maybe?) devoid of trees.

The term "plane folk" is not appropriate in this day and age to people living in (or on) plains; possibly to those who spend a lot of time time in the air, but that's all.

I think it likely that the writer's use of "plane" here has been replaced in more modern writing by "plain", so I don't feel it is right for us to criticise his use of it - or even suggest it should have been in quotes. Or maybe he just confused the two words himself??? I really don't know - I wasn't alive 1n 1884, and I haven't time to follow up the implicit question I pose, sorry!

08:58 Jan 13 

I can see that it would cause confusion, the original writer should have included the words "flatland" and "plane being" in inverted commas the way lorenab23 has pointed out, or at least (and less satisfactorily) put the two words in italics. You might wish to include the punctuation in your translation in order to avoid ambiguity.