including JPEG in SVG

Given the following brain-dead simple SVG:

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE svg
  PUBLIC "-//W3C//DTD SVG 1.0//EN"
"http://www.w3.org/TR/2002/REC-SVG-20010904/DTD/svg10.dtd">

<svg 
    xmlns:xlink="http:///www.w3.org/1999/xlink" 
    width="1275.75pt" height="1179.218269pt" 
    viewBox="0 0 6378.75 5896.091345">

   <image width="250" height="250" xlink:href="test.jpg" />

</svg>


Why am I not seeing the JPEG image?  Both the svg file and jpg file are in
the same directory. It's gotta be some fundamental cluelessness on my part.
I can see the jpg file directly in the browser, and I have the Adobe SVG 3.0
plug-in.