function makeCloud(cloud_no,offsetTop,someDelay){
  var time = 1000 * 60 * 2 + 1000 * 30 * Math.ceil(Math.random() * 6); // + Math.random() * 0.8 * 60 * 2000;
  var top_pos = offsetTop + 50 * Math.random();
  var left_pos = -1000 + Math.ceil(Math.random() * 400);
  var vertMovement = -10 + Math.ceil(Math.random() * 10); //-400 + Math.ceil(Math.random() * 600);
  var vertOffset = (vertMovement >= 0) ? "+="+vertMovement : "-="+Math.abs(vertMovement);
  var cloud_src = "/images/cloud_"+cloud_no+".png";
  var cloud = $("<div />").
    css({position:"absolute", "top":top_pos, "left":"-240px"}).
    delay(someDelay).html("<img src='"+cloud_src+"'>").prependTo("#cloudHolder");
  cloud.animate({left:"+=2000px",top:vertOffset}, time, "linear", function(){
    $(this).remove();
    makeCloud(cloud_no,offsetTop,someDelay);
  });  
}

$(document).ready(function(){
  makeCloud(1,100,1);
  makeCloud(2,275,35000);
  makeCloud(3,400,12000);
  makeCloud(4,20,500);
});