var elems = [];
var current_elem = 0;

function getCurrentElem()
{
  if (current_elem == elems.length-1)
  {
    current_elem = 0;
    return elems[elems.length-1];
  }
  else
  {
    return elems[current_elem++];
  }
}

$(document).ready(function() {
   elems = $('.chunk');
                 
   var elem = getCurrentElem();
   $(elem).show();
                           
   setTimeout(function() { toggle(elem) }, 5000);
});     

function toggle(old) {
  

  $(old).hide();    
  var new_elem = getCurrentElem();
   $(new_elem).toggle('slide', 1000);   


           
  setTimeout(function() { toggle(new_elem) }, 5000);  
}