Twitter bootstrap modal not working

I am new to Twitter Bootstrap. I am working on a modal panel, but it is not being displayed. It fades the screen, but the modal itself does not appear. I have checked the error console, and there are no errors.

My code is inside the <head> tag; I include the scripts like:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript" src="<?php echo $ruadmin ?>js/bootstrap.js"></script>
<script src="<?php echo $ruadmin ?>js/tablesorter/jquery.tablesorter.js"></script>
<script src="<?php echo $ruadmin ?>js/tablesorter/tables.js"></script>

Modal page:

<a data-toggle="modal" href="#myModal" class="btn btn-primary btn-large">Launch demo modal</a>

<!-- Modal -->
<div id="myModal" class="modal hide fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
  <div class="modal-header">
    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
    <h3 id="myModalLabel">Welcome</h3>
  </div>
  <div class="modal-body">
    <p> Hello </p>
  </div>
  <div class="modal-footer">
    <button class="btn" data-dismiss="modal" aria-hidden="true">Close</button>
    <button class="btn btn-primary">Save changes</button>
  </div>
</div>