[jQuery] Text finder in html

[syg6]

I am trying to create a javascript-based text finder using jQuery. I
have a table like this:

<table id="dataTable">
 <tr>
  <td>
   data 1
  </td>
 </tr>
 <tr>
  <td>
   data 2
  </td>
 </tr>
 <tr>
  <td>
   data 3
  </td>
 </tr>
</table>

And I would like to be able to search for a text in any of the <td>s
and highlight it. I tried something like this:

function find()
{
 text = jQuery("#findText").val();
 columns = jQuery("table#dataTable td");

 for (i=0; i<columns.length; i++)
 {
  if (columns[i].innerHTML.indexOf(text) != -1)
  {
   jQuery(columns[i]).addClass("test");
  }
}

I have defined the test style like this:

<style type="text/css">
a.test { font-weight: bold; }
</style>

When I run the script it does nothing. Not sure why. I've debugged it.
jQuery(columns[i]) is an [Object] that has all the normal jQuery
functions -- addClass(), append(), etc. but when I call any of them
nothing happens.

Can someone tell me what I am doing wrong?

Thanks!
Bob