addChild(object);

Hello,
This may sound like a stupid question, but when I use:
var a = parent.addChild(cloud);
a.x=10;
a = parent.addChild(cloud);
a.x=100;
I only get one cloud made at the position (100,y) (or, the last cloud I declare is the only one to show).

How do I add multiples of a movie clip ?

EDIT: I tried using addChild(new cloud) but the compiler says “Call to a possibly undefined method cloud.”

Thanks