How to scroll in an iframe with reference to another url?

Is this not possible?

I tried:

$(".scroll").click(function () {
    var iframe = $('#xframe').contents();
    iframe.scrollTop(400);
});

Above the browser crashes for security

Also:

$(".scroll").click(function () {
    var iframe = $('#xframe');
    iframe.scrollTop(400);
});

The second has no effect