Passages - Moving a marker along a line

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Northwest-Northeast</title>
  
  <meta name='viewport' content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no' />
  <script src='https://api.tiles.mapbox.com/mapbox.js/v1.5.0/mapbox.js'></script>
  <script src='passages.js'></script>
  <link href='https://api.tiles.mapbox.com/mapbox.js/v1.5.0/mapbox.css' rel='stylesheet' />
  
  <style>
    body { margin:0; padding:0; }
    #map { position:absolute; top:0; bottom:0; width:100%; background-color: #000; }
  </style>
</head>
<body>
<div id='map'></div>
<script>
var map = L.mapbox.map('map','landplanner.ln1urf6r', {
  maxZoom:7
}).setView([0, 0], 4);

//var polarbase = L.Mapbox.TileLayer('landplanner.antarctic').addTo(map);

var geojsonLayer = L.geoJson(passages),
    marker = L.marker([0, 0], {
        icon: L.mapbox.marker.icon({'marker-size': 'large', 'marker-symbol': 'ferry', 'marker-color': '0000FF'})
    }).addTo(map),
    j = 0;

tick();
function tick() {
    // set the marker to be at the same point as one of the segments
    // of the line
    marker.setLatLng(L.latLng(
        passages.features[3].geometry.coordinates[j][1],
        passages.features[3].geometry.coordinates[j][0]));

// move to the next point in the line or loop to the first point if
    // j runs off the end of the array
    if (++j < passages.features[3].geometry.coordinates.length) setTimeout(tick, 300);
}
</script>
</body>
</html>

Modified http://api.tiles.mapbox.com/mapbox.js/v1.5.0/mapbox.js to a secure url

https://api.tiles.mapbox.com/mapbox.js/v1.5.0/mapbox.js