They were moved over so the first violins would be on the left and the second violins would be on the right. This is how orchestras used to be arranged until more modern times. Sometimes passages were written with stereo effects in mind for the violins, and unless the second violins are placed there, the effect is lost. This arrangement is becoming more common again.
I'm just watching Christian Thielemann on "Discovering Beethoven" and he is making the exact point made above - that stereo effects were being used back then - with the seperation of the first and second violins. He was discussing the first movement of the Pastoral.
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