var num=0;

imgArray = [
  ['images/Investigations/Invest20090509_01.JPG','Group Photograph','1/11 - Group Photograph'],
  ['images/Investigations/Invest20090509_02.JPG','Light Anomaly','2/11 - Light Anomaly'],
  ['images/Investigations/Invest20090509_03.JPG','Multiple Light Anomalies','3/11 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090509_04.JPG','Multiple Light Anomalies','4/11 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090509_05.JPG','Light Anomaly','5/11 - Light Anomaly'],
  ['images/Investigations/Invest20090509_06.JPG','Multiple Light Anomalies','6/11 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090509_07.JPG','Multiple Light Anomalies','7/11 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090509_08.JPG','Multiple Light Anomalies','8/11 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090509_09.JPG','Multiple Light Anomalies','9/11 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090509_10.JPG','Light Anomaly','10/11 - Light Anomaly'],
  ['images/Investigations/Invest20090509_11.JPG','Light Anomaly','11/11 - Light Anomaly']
]

function slideshow(slide_num) {
  document.getElementById('mypic').src=imgArray[slide_num][0];
  document.getElementById('mypic').alt=imgArray[slide_num][1];
  document.getElementById('burns').innerHTML=imgArray[slide_num][2];
}

function slideshowUp() {
  num++;
  num = num % imgArray.length;
  slideshow(num);
}

function slideshowBack() {
  num--;
  if (num < 0) {num=imgArray.length-1;}
  num = num % imgArray.length;
  slideshow(num);
}