svg figure role

["Chris Chiasson" <chris@chiasson.name>]

Dear docbook-apps,

I am trying to make an svg file appear in xhtml output and a png file
appear in html output. I don't believe I have any profile.role =
blahblah statements in my customization layer or on the command line.
When I order the png image first (along with the html role statement),
both xhtml and html output contain the png file. When I order the svg
image first (along with the xhtml role statement) both xhtml and html
output contain a blank spot where the svg should be. I'm using docbook
xsl 1.69.1.

****What's going on here?? How do I make the svg and xhtml pair up
while also pairing the png and html?? Why isn't the svg rendering at
all?****

note: the files are linked at the bottom.

      <figure>
        <title>Vacuum Flask</title>
        <mediaobject>
          <imageobject role="html">
            <imagedata
fileref="Gravimetric_and_Gasometric_Determination_of_Zinc/Vacuum_Flask.png"/>
          </imageobject>
          <imageobject role="xhtml">
            <imagedata
fileref="Gravimetric_and_Gasometric_Determination_of_Zinc/Vacuum_Flask.svg"/>
          </imageobject>
          <imageobject role="fo">
            <imagedata
fileref="Gravimetric_and_Gasometric_Determination_of_Zinc/Vacuum_Flask.eps"/>
          </imageobject>
        </mediaobject>
      </figure>

Here are links to the relevant files:
http://chris.chiasson.name/Fuel_Cell_Electrochemistry/Fuel_Cell_Electrochemistry.xhtml
http://chris.chiasson.name/Fuel_Cell_Electrochemistry/Gravimetric_and_Gasometric_Determination_of_Zinc/Vacuum_Flask.svg
http://chris.chiasson.name/Fuel_Cell_Electrochemistry/Fuel_Cell_Electrochemistry.html
http://chris.chiasson.name/Fuel_Cell_Electrochemistry/Gravimetric_and_Gasometric_Determination_of_Zinc/Vacuum_Flask.png

Thank you for your help,
--
http://chris.chiasson.name/