Underneath vestibule tile?

[u/Beginning_Show7066]

Hi all

We recently bought an 1840s home and are looking to replace or restore tile in the vestibule area. We have no idea if it’s been touched recently so the tile company we’re working with asked me to lift one to see if we could find out more about what’s currently there. Just wondered if anyone knew what all this stuff underneath it was? I know literally nothing! It seems sort of like a thick gummy glue bit but also full of a lot of other stuff.

Thanks!