jQuery nth-child selector not working

I have a div id (auctions), and I want to swap out the HTML with the children of auction-list. However, jQuery cannot select the children of the auction-list div.

Here's the HTML:

<div id="all">      
    <div id="auctions"></div>
</div>

<div id="auction-list" class="hide">
    <div class="auction">Test</div>
    <div class="auction">Test</div>
</div>

Here's the jQuery:

alert($("#auction-list").children().length);
alert($("#auction-list").html());
alert($("#auction-list:nth-child(1)").html());
alert($("#auction-list:nth-child(2)").html());
$("#auctions").html($("#auction-list:nth-child(1)").html());

And here are the outputs for the Javascript alerts:

First Alert

2

Second Alert

<div class="auction">Test</div>
<div class="auction">Test</div>

Third Alert

null

What am I overlooking here?