occurred to me, it did, that I will be replacing the cavity with a smaller cavity, much smaller.  the new cavity will be as wide and as tall as the former one, but will be only a few inches deep… plus the interior dimensions of the wall itself.

I am going to put some things inside of it.  the first thing that came to mind, since I had recently handled it, was the New Atla/ntis festival program.  but various other things could go in the cavity before I reseal it.  printed material and such for a future inhabitant to discover.   I might live here for a long time, and I presume my remodeling will be so effective and universally pleasing that the cavity will not be re-opened for maybe another 50 or 100 years or so, unless there is some kind of upstairs plumbing disaster or such.  hard to say.

I might make a simple website with a login form and include the username/password in a note in the cavity.  I could set it up to email me when someone logs in.

I don’t know how long it will be until I’m able to reseal the new, smaller  cavity.  it shouldn’t be more than a month or so from now, I hope.   if you’d like me to put something inside, feel free to mail or email it to me, or post a comment.  one page max.  I suppose I could set up the futurecavity website to email you and/or your progeny if you like.  I don’t know about the logistics of keeping a website online for a long time, but I’m sure there’s a way it can be done cheaply and reliably.  keeping it online during my lifetime is easy enough, as it can just piggyback on whatever is my hosting account at the time.  I would have to make add’l arrangements for posthumous hosting but I’m sure there’s a way.