How did bridge builders of old ensure both ends of the bridge would perfect meet in the middle before laser measuring was around?

Question

How did bridge builders of old ensure both ends of the bridge would perfect meet in the middle before laser measuring was around?

In: Engineering

Answer 1

I’d ask the same question about *tunnels*. You can’t even see where you’re headed.

IIRC there’s some tunnel connecting Manhattan with either New Jersey under the Hudson River or Brooklyn under the East River (I don’t remember what side) that was built in the late 1800s with two excavation teams from both sides that met in the middle with an error of less than 1 inch. I can’t get through my skull how this could be done at the time.