function show(num)
		  {
				var trArr=new Array('river1','river2');
				var divArr=new Array('con_r1','con_r2');
				var tp1=new Array('images/t_n01.gif','images/t_n02.gif');
				var tp2=new Array('images/t_n1.gif','images/t_n2.gif');
				for(i=0;i<2;i++)
				{
					if(i==num)
					{
						eval("document.getElementById(trArr[i]).src=tp1[i];");
						eval("document.getElementById(divArr[i]).style.display='block';");
					}
					else
					{
						eval("document.getElementById(trArr[i]).src=tp2[i];");
						eval("document.getElementById(divArr[i]).style.display='none';");
					}
				}
		  }