jQuery using arrow key scrolling during presentation

I'm creating a presentation using HTML for a project I'm working on. The presentation will be full-page slides and I want to implement a script with jQuery so that when the arrow keys are pressed, it scrolls smoothly between slides. Left being previous slide and right being next slide obviously.

I wrote a script but it only works the first time. I'm very new to jQuery and I can't seem to fix it.

The page the presentation will be on is: http://ift.tt/1ekJPbP

<script type="text/javascript">
$(document).keydown(function(e){
if (e.keyCode == 37) { 
   $('.slide').previous().ScrollTo({
        duration: 2000,
        easing: 'linear'
    });
}
if (e.keyCode == 39) { 
   $('.slide').next().ScrollTo({
        duration: 2000,
        easing: 'linear'
    });
    }
});
</script>