var numImages = 4;
var currentImage = 1;
imageInterval = window.setInterval("changeImage();", 7500);
function changeImage()
{
        $("#img" + currentImage).fadeOut("slow", function() {
                if (currentImage >= numImages)
                {
                        currentImage = 0;
                }
                $("#img" + (currentImage + 1) ).fadeIn("slow", function() {
                        currentImage++;
                });
        });
}