$(document).ready(function() {
  $('div.button').click(function() {
    var $speech = $('div.speech');
    var currentSize = $speech.css('fontSize');
    var num = parseFloat( currentSize, 10 );
    var unit = currentSize.slice(-2);
    if (this.id == 'switcher-large') {
      num *= 1.4;
    } else if (this.id == 'switcher-small') {
      num /= 1.4;
    }
    $speech.css('fontSize', num + unit);
  });
});