My slider just won't show up

Unity Engine
1

I am trying to ceate a slider, but it just doesnt show up.
my script is:

public class gyro : MonoBehaviour {
float slidervalue;
void OnGui() {
Rect slider = new Rect (0, 0, 100, 30);
slidervalue = GUI.HorizontalSlider(slider,slidervalue,1.0f,100.0f);
}
void Update(){
Debug.Log (slidervalue);
}
}

The slider just inst there. I have the gui layer and this script on the camera, but it doesnt work anywhere for me.
It has to be just some kind of dumb mistake.

2

OnGui needs to be OnGUI