about the midnight sun
`` Yes , yes ; but I do n't mean your book , my lad . I mean the geography and knowledge in your head . Do n't you remember that the farther we go north at this time of year the lighter it becomes , till , not many miles farther , it will be all daylight ? '' `` Yes , I remember now , '' cried Steve ; `` but it 's rather puzzling , all that about the midnight sun . Does n't the sun really set at all ? '' `` No , '' said Captain Marsham , smiling at the lad 's puzzled expression . `` Then what does it do ? ''