"No, Watson, I fear that I could not undertake to recognize your footprint amid all the footprints of the world. 

If you seriously desire to deceive me you must change your tobacconist; for when I see the stub of a cigarette marked Bradley, Oxford Street, 

I know that my friend Watson is in the neighbourhood. You will see it there beside the path. You threw it down, no doubt, at that supreme moment when you charged into the empty hut."

"Exactly."

"I thought as much -- and knowing your admirable tenacity I was convinced that you were sitting in ambush, a weapon within reach, waiting for the tenant to return. So you actually thought that I was the criminal?"

麻烦老师讲一下I thought as much 中的as much这里究竟是什么意思，什么用法？