Prototype's "down" method is unavailable

A Blue Ridge user reported an issue when using Prototype's "Element.down()" method. http://github.com/relevance/blue-ridge/issues#issue/6

I've added a failing "down method" test to the test/unit/prototypecompat.js file. When it passes, this ticket is closed. Here's the test snippet that crashes:

test("down method", function(){
expect(1);
ok($('main').down('#foo') != undefined, "$('main').down('#foo') successfully found an element"); });