$(document).ready(function() {

        var speed = 1000,
            interval = 4000,
            stage_left = $('#slideshow-left'),
            stage_right = $('#slideshow-right'),
            toggle, i;

        for (i=1; i<=7; i++) {
            $('<div>')
                .attr('id', 'slideshow-left-' + i)
                .appendTo($('#slideshow-left'));

            $('<div>')
                .attr('id', 'slideshow-right-' + i)
                .appendTo($('#slideshow-right'));
        }

        $('.slideshow div').addClass('ready');
        window.setInterval(on_timer, interval);

        function on_timer() {
            if (toggle == 'right') {
                toggle = 'left';
                do_slide(stage_right);
            } else {
                toggle = 'right';
                do_slide(stage_left);
            }
        }

        function do_slide(stage) {
            var slides = $('div', stage),
                current = $(slides.get(0)),
                next = $(slides.get(1));

            next.fadeIn(speed, function() {
                    current.hide();
                    current.appendTo(stage);
                });
        }

});