Infinite Scrolling in Kaminari

I use Kaminari for pagination. And here is the code that I use for infinite scrolling:

jQuery(function() {
   if ($('.pagination').length) {
     $(window).scroll(function() {
       var url;
       url = $('.pagination .next_page').attr('href');
       if(url && $(window).scrollTop()>$(document).height()-$(window).height()-50)
       {
         $('.pagination').text("Fetching more products...");
         return $.getScript(url);
       }
    });
    return $(window).scroll();
}

The above code I wrote in the document.ready function. And then this code is written in the .js.erb file

$("#container1").append("<%= escape_javascript(render 'shirts/first')%>");
    <% if @first.next_page %>
       $('.pagination').replaceWith("<%= j paginate @first %>");
    <% else %>
       $('.pagination').remove();
    <% end %>
    <% sleep 1 %>
});

But I do not get an endless scroll. Can someone direct me to where I am wrong?