var c=$(this),ul=$("ul",c)，这个变量ul是什么？
在 jCarouselLite 无缝滚动插件中，看到的如下定义，但是没有看懂，谁能解释下，谢谢.

// JavaScript Document

(function($){

	$.fn.jCarouselLite=function(o){

		o=$.extend({

			maxSize:null,btnPrev:null,btnNext:null,btnGo:null,mouseWheel:false,auto:null,speed:200,easing:null,vertical:false,circular:true,visible:3,start:0,scroll:1,beforeStart:null,afterEnd:null

		}

		,o||{});

		return this.each(function(){

			var b=false,animCss=o.vertical?"top":"left",sizeCss=o.vertical?"height":"width";

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   就是下面这行代码 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

			var c=$(this),ul=$("ul",c),tLi=$("li",ul),tl=tLi.size(),v=o.visible;

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   没有看懂这个变量 ul=$("ul",c)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

			if(o.circular){

				ul.prepend(tLi.slice(tl-v-1+1).clone()).append(tLi.slice(0,v).clone());

				o.start+=v

			}

			var f=$("li",ul),itemLength=f.size(),curr=o.start;

			c.css("visibility","visible");

			f.css({

				overflow:"hidden",float:o.vertical?"none":"left"

			});

			ul.css({

				margin:"0",padding:"0",position:"relative","list-style-type":"none","z-index":"1"

			});

			c.css({

				overflow:"hidden",position:"relative","z-index":"2",left:"0px"

			});

			var g=o.vertical?height(f):width(f);

			var h=g*itemLength;

			var j=g*v;

			if(o.maxSize != null) j = j> o.maxSize?o.maxSize:j;

			f.css({

				width:f.width(),height:f.height()

			});

			ul.css(sizeCss,h+"px").css(animCss,-(curr*g));

			c.css(sizeCss,j+"px");

			if(o.btnPrev)$(o.btnPrev).click(function(){

				return go(curr-o.scroll)

			});

			if(o.btnNext)$(o.btnNext).click(function(){

				return go(curr+o.scroll)

			});

			if(o.btnGo)$.each(o.btnGo,function(i,a){

				$(a).click(function(){

					return go(o.circular?o.visible+i:i)

				})

			});

			if(o.mouseWheel&&c.mousewheel)c.mousewheel(function(e,d){

				return d>0?go(curr-o.scroll):go(curr+o.scroll)

			});

			if(o.auto)setInterval(function(){

				go(curr+o.scroll)

			}

			,o.auto+o.speed);

			function vis(){

				return f.slice(curr).slice(0,v)

			};

			function go(a){

				if(!b){

					if(o.beforeStart)o.beforeStart.call(this,vis());

					if(o.circular){

						if(a<=o.start-v-1){

							ul.css(animCss,-((itemLength-(v*2))*g)+"px");

							curr=a==o.start-v-1?itemLength-(v*2)-1:itemLength-(v*2)-o.scroll

						}

						else if(a>=itemLength-v+1){

							ul.css(animCss,-((v)*g)+"px");

							curr=a==itemLength-v+1?v+1:v+o.scroll

						}

						else curr=a

					}

					else{

						if(a<0||a>itemLength-v)return;

						else curr=a

					}

					b=true;

					ul.animate(animCss=="left"?{

						left:-(curr*g)

					}

					:{

						top:-(curr*g)

					}

					,o.speed,o.easing,function(){

						if(o.afterEnd)o.afterEnd.call(this,vis());

						b=false

					});

					if(!o.circular){

						$(o.btnPrev+","+o.btnNext).removeClass("disabled");

						$((curr-o.scroll<0&&o.btnPrev)||(curr+o.scroll>itemLength-v&&o.btnNext)||[]).addClass("disabled")

					}

				}

				return false

			}

		})