Google Map Marker Help


I am using the Google Maps V3 API and have my map working.

Basically I want a few markers to be shown at ever zoom level.

Then from zoom level 8 onwards I want more markers to be added.

I know it can be done using the Google Maps Marker Manager but I really cannot get it to work.

Please can someone have a look and try to give me a hand:

// Set up map on home index page
  if ($('body').hasClass('home')) {
    // Define map centre as world over view
    var worldCenter = new google.maps.LatLng(33.4, -5);
    // Set up homeMap options
    var homeMapOptions = {
      scrollwheel: false,
      zoom: 2,
      center: worldCenter,
      mapTypeId: google.maps.MapTypeId.TERRAIN
    // Display map on page
    var homeMap = new google.maps.Map($('.home .map')[0], homeMapOptions);
    // Set up a markerManager and apply it to the homeMap
    var mgr = new MarkerManager(homeMap);
    //Show all Parks as markers on homeMap
    // Make json request and run a function with all parks in the parks object
    $.getJSON('parks.json', function(parks) {
      // Set up an infoWindow
      var infoWindow;
      // For each park...
      $.each(parks, function(key, park) {
        // Set a location variable
        latlng = new google.maps.LatLng(, park.long);
        // Create a marker for the current park and put it on the map
        var marker = new google.maps.Marker({
          position: latlng, 
          map: homeMap,
        // Add the current marker to the marker manager with a minimum zoom level of 5
        mgr.addMarker(marker, 2);
        // Refresh the marker manager

Currently, no markers even appear on the map.

Please help