I think there's no such thing as a solid foundation. Buildings sink (and often rise) over time, often differentially, as the ground becomes compacted over a long period - or heaves as the water table or temperature changes - or these things happen repeatedly over different seasons and the sockets wear loose. And then there's Darwin observing fallen stones sinking into the ground due to worms.

How much of all that they were aware of is a moot point though.