var num=0;

imgArray = [
  ['images/Investigations/Invest20090207_01.JPG','Is this a face in the window?','1/13 - Is this a face in the window?'],
  ['images/Investigations/Invest20090207_02.JPG','Light Anomaly','2/13 - Light Anomaly'],
  ['images/Investigations/Invest20090207_03.JPG','Light Anomaly','3/13 - Light Anomaly'],
  ['images/Investigations/Invest20090207_04.JPG','Light Anomaly','4/13 - Light Anomaly'],
  ['images/Investigations/Invest20090207_05.JPG','Light Anomaly','5/13 - Light Anomaly'],
  ['images/Investigations/Invest20090207_06.JPG','Light Anomaly','6/13 - Light Anomaly'],
  ['images/Investigations/Invest20090207_07.JPG','Multiple Light Anomalies','7/13 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090207_08.JPG','Multiple Light Anomalies','8/13 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090207_09.JPG','Multiple Light Anomalies','9/13 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090207_10.JPG','Multiple Light Anomalies','10/13 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090207_11.JPG','Multiple Light Anomalies','11/13 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090207_12.JPG','Multiple Light Anomalies','12/13 - Multiple Light Anomalies'],
  ['images/Investigations/Invest20090207_13.JPG','Light Anomaly','13/13 - 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);
}