var fade_speed = 250;

$(document).ready(function() {
	$("div.slide").hover(overlay_on, overlay_off);
});
function overlay_on() {
	$(this).children("div.image").animate({opacity: 0.4}, fade_speed);
}
function overlay_off() {
	$(this).children("div.image").animate({opacity: 1}, fade_speed);
}