Was thinking today with my hands about what a lot of work it is to build a dry stone bridge. Here is an amazing picture of the beautiful bridge DSWA Mastercraftsman Norman Haddow built in Scotland about ten years ago. The burn (Scottish word for creek) is in flood and actually going around the bridge, yet it stands firm and unmoving 6 years later. The fact that it is not made of solid concrete and can let some water through it must contribute to its strength against the force of the water.
I thought too of the amount of time and effort and stone that went into building Cornish Hollow Bridge, a small roman arch dry stone bridge which DSWAC members constructed in July of 2007 north of Cobourg Ontario. This bridge was the second one we built after having Norman Haddow come here from Scotland and teach us about bridge construction at Hill and Dale B&B in Port Hope Ontario where ten members of the DSWAC built a six foot span dry stone packhorse bridge. Leigh Bamford and I were involved in both bridge projects.
We used up over 40 tons of stone in the building of Cornish Hollow bridge which had a whopping 12 foot span. That's a lot material. In comparison, however I was considering the amount of water that has gone under it since the day it was built over four years ago.
This represents a huge volume, as you can see the bridge is actually built in a flood plane and sometimes in spring run off water has to go around it as well. And yet even with it having had so much water go under it , if were it to fall down, even in say, the next fifty years, that wouldn't have been enough water, would it ? The life time of the bridge would still have been too short for the volume of water that the builders expected would flow under it. The bridge would not be considered to have been a success either.
Even though the bridge may have done a great job and allowed water to flow unobstructed and unnoticed, it would still not be enough water to not make a big thing about it 'not lasting'.
I think that it is fair to say however that concerning bridges, if we were going to use an expression like 'that's all water under the bridge' we should be referring to a long enough lapse of time (relative to the normal lifetime of a properly built bridge, perhaps) so that certain things we have done or said in the past that we were hoping to merely 'dismiss', reflects an understanding of just how much time and water we are talking about.