What do Four Vertical Dots mean?

Question

I was looking through a score by Bartok (5th String Quartet) and came across a symbol I didn't recognize. There is a dot between each line in the clef.

What does this mean?

Edit: Here's another example, which looks more like a barline:

Answer 1

In this particular quartet, the solid bar lines are being used for coordination, but the instruments themselves are following their own metres which are demarcated by the dotted bar lines: the music is polymetric. The beaming across the bar line confirms this interpretation.

In the first example, the first violin is counting 4/8, 5/8, 3/8, 4/8; the 2nd violin is counting 4/8, 5/8, 7/8; and the viola and 'cello are counting 6/8, then two bars of 5/8. (The interpretation of each instrument's first and last "bars" might change depending on what precedes and follows the example.)

In the second example, the first and second violins are completing a "bar" with their first two quavers, then following with two bars of 7/8; the viola and 'cello are beating 5/8, 4/8 and 7/8.

Answer 2

This sort of notation normally means a "semi-barline". I have seen it where (e.g.) a 4/4 bar is divided into two halves by a dotted barline, meaning "It's in 4/4, but well you might also feel it in 2/4".

This example is a bit more difficult, but then it is Bartok. I would guess that the parts are supposed to "feel" the tempo divided into different ways.

But you needn't take my word for it: Gardner Read calls them "dotted barlines", and even discusses the Bartok string quartet no. 5, which divides up the different parts in just this way.