Getting the first image elements id within an unordered list using JQuery

I'm trying to get the id of the first element of an unordered list using JQuery.

Here's the list

<ul class="list">
<li><img id="1" src="开发者_JAVA百科image1.jpg" name="image1" /></li>
<li><img id="2" src="image2.jpg" name="image2" /></li>
<li><img id="3" src="image3.jpg" name="image3" /></li>
<li><img id="4" src="image4.jpg" name="image4" /></li>
<li><img id="5" src="image5.jpg" name="image5" /></li>
</ul>

JQuery

var id = $('.list li img'):first.attr('id');

Close.

var id = $('.list li img:first').attr('id');