 But that efflorescence on the outside is really a signal to you that you got something going on. What could it be? Well, it can certainly be missing mortar up there. Maybe that chimney's been there 35 years and the mortar's cracked and got water in it. It froze. It cracked some more. You know what I'm speaking of. And it doesn't take much of a crack. Or maybe some of the mortar's actually fallen out and you can get your finger into it.