var imageFiles_ch_1 = new Array();
imageFiles_ch_1['0'] = new Array ('_images/ch_Contact_Us.gif', '_images/ch_Contact_UsMouseover.gif');
imageFiles_ch_1['1'] = new Array ('_images/ch_Butterfly_House.gif', '_images/ch_Butterfly_HouseMouseover.gif');
imageFiles_ch_1['2'] = new Array ('_images/ch_Links.gif', '_images/ch_LinksMouseover.gif');
imageFiles_ch_1['3'] = new Array ('_images/ch_Articles.gif', '_images/ch_ArticlesMouseover.gif');

function image_on_ch_1 (position) {
   var doc = eval("document.imagech_1" + position);
   doc.src = imageFiles_ch_1[position][1];
}

function image_off_ch_1 (position) {
   var doc = eval("document.imagech_1" + position);
   doc.src = imageFiles_ch_1[position][0];
}