Finding the Offset of a

PROBLEM: Can't get the offset of a <frame> using jQuery (v2.1.3) + phantomJs (v2.0) because $('frame') can't find any frame.

QUESTION: How can I access the offset of the 2nd frame in the page?

DETAILS: I'm running a phantomjs script to access a webpage (link) and fetch a specific Captcha image. The markup of the page is:

<frameset>
    <frame></frame>
    <frame>The image is inside this frame!</frame>
</frameset>

And the image that I'm searching for is inside the second <frame> and it has an id of #imgCaptcha. I'm using this script (which is not working) to try to get the offset of the frame:

page.open(url, function (status) {

    console.log("Status: " + status);
    if (status === "success") {
        page.render('example.png');
    } else {
        phantom.exit();
    }

    page.includeJs('http://ift.tt/1vhyxae', function () {
        var frame_offset = page.evaluate(function () {
            var frame_offset = [];
            $('frame').each(function () {
                frame_offset.push($(this).offset().top);
            });
            return frame_offset;
        });
        console.log(frame_offset.length);
    });
    phantom.exit();
});

I'm also running the following error handling functions (callback functions): onResourceError ,onError ,onResourceTimeout ,onConsoleMessage . However, they don't display any information (no error).

Thanks for helping!!!! :DDD