Easing options not working

Easing options not working

I have created a horizontal image slider - it shows 3 images and then after a set period of time the images slide to the left. The first image (that just moved off "screen"is then moved to the bottom of the list of images. So the images continue to loop indefinitely which is what i am wanting. 

What is not working for me is the speed at which the animation occurs - it is too fast and I would like the movement of the images to the left to be slower and smoother. I have tried easing options but they seem to have no effect.

Here is the query code and the html it is referring to: - this is saved and linked as scroller.js

$(document).ready(function(){
  function rotate() {
 $('.slideshow1 img').first().animate({left:'300px'},2000, "easeOutCubic", function() {
 $(this).insertAfter($('.slideshow1 img').last()).show();  
 });
  }
  setInterval(function() {
 rotate();
  },3000);
});

<div class="slideshow1">
  <img class="show" src="images/slideshow images/10-attractive-container-gardening-ideas-fine-gardening-min.jpg">
  <img class="show" src="images/slideshow images/barrow-and-gumboots-min.jpg">
  <img class="show" src="images/slideshow images/container-garden-wheelbarrow-flowers-min.jpg">
  <img src="images/slideshow images/flowers-and-fork-min.jpg">
  <img src="images/slideshow images/gardening_campers-min.jpg">
  <img src="images/slideshow images/grandma-and-child-min.jpg">
  <img src="images/slideshow images/tulips-min.jpg">
</div>

I have linked to libraries as follows:

<script src="scripts/jquery-1.11.1.min.js"></script>
<script src="scripts/jquery-migrate-1.2.1.min.js"></script>
<script src="scripts/jquery-ui-1.11.1.custom/jquery-ui-1.11.1.custom/jquery-ui.js"></script>
<script src="scripts/scroller.js"></script>