Find biggest number in an array

Hello.
How can I find the biggest number in an array? And display it with an alert function?
Here's my javascript:

$(document).ready(function() {
$("#array").click(function() {
var numbers = new Array["1", "7", "10", "12", "15"]
var max_of_array = Math.max.apply(Math, array);
alert(arr.max());
});
});

/Thanks